I have Windows 7 Ultimate OS. I'm opening mmc.exe as administrator and trying add Certificates or any other snap-in, then while loading that snap-in MMC breaks and displays following message and after that it closes automatically once I click on close button on that message. What could be the problem? I did following to fix the problem but couldn't succeed any of these: I tried to repair the OS I repaired files using this method Even repaired the installation using this link Update: *@oldskool: Here is the debug process output:* Sorry its a long output text. 'mmc.exe': Loaded 'C:\Windows\System32\mmc.exe', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\ntdll.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\kernel32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\KernelBase.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\gdi32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\user32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\lpk.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\usp10.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\msvcrt.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\mfc42u.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\ole32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\rpcrt4.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\oleaut32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\odbc32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\advapi32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\sechost.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\mmcbase.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\shlwapi.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\uxtheme.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\duser.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\imm32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\msctf.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\odbcint.dll', Binary was not built with debug information. 'mmc.exe': Loaded 'C:\Windows\System32\dui70.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\winsxs\x86_microsoft.windows.common-controls_6595b64144ccf1df_6.0.7600.16661_none_420fe3fa2b8113bd\comctl32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\shell32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\cryptbase.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\urlmon.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\wininet.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\iertutil.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\crypt32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\msasn1.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\clbcatq.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\mmcndmgr.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\dwmapi.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\oleacc.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\cryptsp.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\rsaenh.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\RpcRtRemote.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\mlang.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\xmllite.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\version.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\apphelp.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\msi.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Program Files\Microsoft Visual Studio 8\SDK\v2.0\Bin\mscormmc.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\mscoree.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\winsxs\x86_microsoft.vc80.crt_1fc8b3b9a1e18e3b_8.0.50727.4927_none_d08a205e442db5b5\msvcr80.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\azroleui.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\atl.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\secur32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\netutils.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\dsrole.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\logoncli.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\dsuiext.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\ntdsapi.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\ws2_32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\nsi.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\activeds.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\adsldpc.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\Wldap32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\mpr.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\netapi32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\srvcli.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\wkscli.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\certmgr.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\certcli.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\CertEnroll.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\cryptui.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\ncrypt.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\bcrypt.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\wintrust.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\imagehlp.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\sspicli.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\aclui.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\IPHLPAPI.DLL', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\winnsi.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\slc.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\comsnap.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\mfc42.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\mycomput.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\devmgr.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\setupapi.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\cfgmgr32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\devobj.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\devrtl.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\newdev.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\dmdskmgr.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\dmutil.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\dmdskres.dll', Binary was not built with debug information. 'mmc.exe': Loaded 'C:\Windows\System32\dmdskres2.dll', Binary was not built with debug information. 'mmc.exe': Loaded 'C:\Windows\System32\gpedit.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\dssec.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\authz.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\dfscli.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\samcli.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\gpapi.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\framedynos.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\wtsapi32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\ipsmsnap.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\winipsec.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\userenv.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\profapi.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\ipsecsnp.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\polstore.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\localsec.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\wdc.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\pdh.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\pdhui.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\comdlg32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\credui.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\wevtapi.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\pla.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\tdh.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\winsta.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\utildll.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\browcli.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\vdmdbg.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\pmcsnap.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\winspool.drv', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\puiapi.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\wsecedit.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\scecli.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\filemgmt.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Program Files\Microsoft SQL Server\100\Tools\Binn\SqlManager.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\winsxs\x86_microsoft.vc80.mfc_1fc8b3b9a1e18e3b_8.0.50727.4053_none_cbf21254470d8752\mfc80u.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\winsxs\x86_microsoft.vc80.crt_1fc8b3b9a1e18e3b_8.0.50727.4927_none_d08a205e442db5b5\msvcp80.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\winsxs\x86_microsoft.vc80.atl_1fc8b3b9a1e18e3b_8.0.50727.4053_none_d1c738ec43578ea1\ATL80.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\winsxs\x86_microsoft.windows.common-controls_6595b64144ccf1df_5.82.7600.16661_none_ebfb56996c72aefc\comctl32.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\winsxs\x86_microsoft.vc80.mfcloc_1fc8b3b9a1e18e3b_8.0.50727.4053_none_03ca5532205cb096\mfc80ENU.dll', Binary was not built with debug information. 'mmc.exe': Loaded 'C:\Program Files\Microsoft SQL Server\100\Tools\Binn\Resources\1033\SqlManager.rll', Binary was not built with debug information. 'mmc.exe': Loaded 'C:\Windows\System32\msxml6.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Program Files\Microsoft SQL Server\90\Tools\Binn\SqlManager.dll', Cannot find or open the PDB file 'mmc.exe': Loaded 'C:\Windows\System32\wbem\wbemcntl.dll', Cannot find or open the PDB file The thread 'Win32 Thread' (0xf74) has exited with code 0 (0x0). Unhandled exception at 0x774d35e3 in mmc.exe: 0xC0000374: A heap has been corrupted.