1. Open C:WindowsMicrosoft.NETFrameworkv3.5Microsoft.CompactFramework.Common.targets
2. Find paragraph:
<Target Name="PlatformVerificationTask"> <PlatformVerificationTask PlatformFamilyName="$(PlatformFamilyName)" ... </Target>
3. Change one line as below, thus disabling platform verification:
<Target Name="PlatformVerificationTask" Condition="0==1"> <PlatformVerificationTask PlatformFamilyName="$(PlatformFamilyName)" ... </Target>
4. Restart VS2008. Problem solved