Class library set to .NET 2.0 is building to .NET 4.0

I have a web solution that contains 5 class libraries and one asp.net web site project. It's an e-commerce solution that is compiled for .NET 3.5 (some class libraries are set to .NET 2).

When I got VS 2010 installed I decided to give a try and upgrading it to .NET 4 but that didn't go so well, can't remember why. I reverted the source 开发者_开发百科code control, cleared all local files, re-downloaded from source control and went back to VS 2008.

I decided to give it another try with VS 2010 due to some issues with VS 2008 but when I build the solution it fails because one of the class libraries is compiling to .NET 4. I checked the project settings and it is set to .NET 2. I have tried doing a clean on the solution, that makes no difference, the project always builds the assembly to .net framework 4.x.

I imagine something is getting cached on the system, i.e. msbuild, etc. Does anyone know where to clear this cache so that whatever is holding my class library hostage to .net 4 can actually let it completely recompile and pick up the project settings again?

Thank you.

This was a problem in the project file having the Tools attribute set which just needed to be cleared for .NET 4 compilation.