How should I migrate my managed DirectX programs to Windows 7?

Question

Recently I got a new PC with Windows 7 and installed C# 2010 Express. I have a LOT of software I wrote on my Vista machine in C# 2008 Express. When I tried to migrate the managed D3D apps to 2010, they all crashed on run with an error "is not a valid Win32 application." and after some troubleshooting I learned it's because MS no longer supports managed DirectX. What a drag. So it looks like I'll have to rewrite a ton of code to use one of the following alternatives:

*XNA
*Direct3D 10/11 API (like you would use in VC++)
*OpenGL
*Some other option, like maybe SlimDX

I'm looking for a solution that is:
*Backwards-compatible (ie, Vista and XP)
*Forwards compatible (I don't want to learn a new system just to have to drop it and learn another one in a year)
*OO-friendly -- I have thousands of lines of code to rewrite. I don't have a problem writing unmanaged code, but a similar OO solution would probably reduce the porting time.

I can't be the first person to run into this issue. What are some solutions other people found?

Answer 1

My guess would be that your applications are built as AnyCPU, referencing x86 assemblies, but your Win7 machine is x64. Building your applications as x86 might solve the issue.