I have some encrypted pdf files that have no problem and in my last windows, I could open them easily with Adobe Reader 9.2 and other pdf readers.

But now, I can only open non-encrypted pdf files and one encrypted file with Adobe Reader. every time I open almost any encrypted pdf, it closes itself.

Also, when I try to search a folder for a keyword with Foxit Reader, once it closed.

This is not related to Adobe Reader, because I have the same problem with Word 2007. When I open a document, sometimes it closes instantly and sometimes it closes after a few seconds and sometimes it is stable.

My windows is Fresh. I have installed it a few days ago. I have ESET Smart Security 5.2 and I have updated it today.

OS: XP Pro SP3, RAM: 3 GB, CPU: 2 GHZ, HDD: 320 GB

My installed applications:

Adobe AIR
Adobe Flash Player 11 ActiveX
Adobe Flash Player 11 Plugin
Adobe Photoshop CS4
Adobe Reader 9.2
Atheros Wireless LAN Client Adapter
Babylon
Bluetooth Stack for Windows by Toshiba
CCleaner
Conexant HD Audio
Dell Touchpad
ESET Smart Security
Farsi (101) Custom
Foxit Reader
Framing Studio 3.27
Google Chrome
Hard Disk Sentinel PRO
HDAUDIO Soft Data Fax Modem with SmartCP
Intel(R) Graphics Media Accelerator Driver
IrfanView (remove only)
Java(TM) 6 Update 18
K-Lite Mega Codec Pack 8.8.0
Microsoft .NET Framework 2.0 Service Pack 1
Microsoft .NET Framework 3.0 Service Pack 1
Microsoft .NET Framework 3.5
Microsoft Data Access Components KB870669
Microsoft Office 2007 Primary Interop Assemblies
Microsoft Office Enterprise 2007
Microsoft User-Mode Driver Framework Feature Pack 1.0.0 (Pre-Release 5348)
Mozilla Firefox 7.0.1 (x86 en-US)
Notepad++
Office Tab FreeEdition 8.50
ParsQuran
PerfectDisk 12 Professional
Registry First Aid
RICOH R5C83x/84x Flash Media Controller Driver Ver.3.54.06
Sahar Money Manager 2.5
Stickies 7.1d
The KMPlayer (remove only)
TurboLaunch 5.1.2
Unlocker 1.9.1
USB Safely Remove 4.2
Virastyar
Visual Studio 2005 Tools for Office Second Edition Runtime
Winamp
Windows Internet Explorer 8
Windows Media Player 11.0.5358.4826
Windows XP Service Pack 3
WinRAR 4.11 (32-bit)
WorkPause 1.2
Z Dictionary

My startup applications:

WorkPause
USB Safely Remove
TurboLaunch
SunJavaUpdateSched
Stickies
rfagent
Persistence
ParsQuran Daily Verse
ITSecMng
IgfxTray
HotKeysCmds
Hard Disk Sentinel
egui
disable shift+delete
CTFMON.EXE
Bluetooth Manager
Babylon Client
Apoint
AdobeCS4ServiceManager
Adobe Reader Speed Launcher
Adobe ARM

What should I do to solve it? If you recommend installing Windows again, what guarantees that it won't happen again?