Hi, since upgrading my project to VS2010, including the use of MSBuild v4 instead of 3.5 (and not making any other changes), I get the following build error and have no clue how to fix it (log from CC.NET): <target name="ResolveComReferences" success="false"> <message level="high"><![CDATA[C:\Programme\Microsoft SDKs\Windows\v7.0A\bin\TlbImp.exe c:\Assemblies\NMSDVDXU.dll /namespace:NMSDVDXLib /machine:X64 /out:obj\x64\Release\Interop.NMSDVDXLib.dll /sysarray /transform:DispRet /reference:c:\Assemblies\Bass.Net.dll /reference:c:\Assemblies\LogicNP.FileView.dll /reference:C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\mscorlib.dll /reference:C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Data.dll /reference:C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Design.dll /reference:C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.dll /reference:C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Drawing.dll /reference:C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Management.dll /reference:C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Windows.Forms.dll /reference:C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Xml.dll /reference:C:\WINDOWS\assembly\GAC\stdole\7.0.3300.0__b03f5f7f11d50a3a\stdole.dll ]]></message> <error code="TI0000" file="TlbImp"><![CDATA[A single valid machine type compatible with the input type library must be specified.]]></error> <warning code="MSB3283" file="C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets" line="1558" column="9"><![CDATA[Die Wrapperassembly für die Typbibliothek "NMSDVDXLib" wurde nicht gefunden.]]></warning> <message level="high"><![CDATA[C:\Programme\Microsoft SDKs\Windows\v7.0A\bin\TlbImp.exe c:\Assemblies\StarBurnX12.dll /namespace:RocketDivision.StarBurnX /machine:X64 /out:obj\x64\Release\Interop.RocketDivision.StarBurnX.dll /sysarray /transform:DispRet /reference:c:\Assemblies\Bass.Net.dll /reference:c:\Assemblies\LogicNP.FileView.dll /reference:C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\mscorlib.dll /reference:C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Data.dll /reference:C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Design.dll /reference:C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.dll /reference:C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Drawing.dll /reference:C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Management.dll /reference:C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Windows.Forms.dll /reference:C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Xml.dll /reference:C:\WINDOWS\assembly\GAC\stdole\7.0.3300.0__b03f5f7f11d50a3a\stdole.dll ]]></message> <error code="TI0000" file="TlbImp"><![CDATA[A single valid machine type compatible with the input type library must be specified.]]></error> <warning code="MSB3283" file="C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets" line="1558" column="9"><![CDATA[Die Wrapperassembly für die Typbibliothek "RocketDivision.StarBurnX" wurde nicht gefunden.]]></warning> </target> Problem: A single valid machine type compatible with the input type library must be specified. It only applies to the x64 build of my project, x86 still works fine. Apparently, it tries to build a x64 interop assembly from the x86 DLL located in "C:\Assemblies". When executing the TlbImp command with the x64 DLL which is located in a different directory, it works fine. However, I don't know how I can configure my project to use different COM references for the x86 and x64 build. The OS on which the project is being compiled is WinXP x86. Building worked fine when using VS2005 + MSBuild 3.5 Any help would be highly appreciated. I tried building the upgraded project with MSBuild v3.5, but that doesn't work either. It complains about unknown NoWarn codes (probably new in 4.0).