64 bit computer, 64 bit VC++ express 2010, then why?

I am running into this issue:

warning : Platform 'x64' referenced in the project file 'xyz' cannot be found. Please make sure you have it installed under '%VCTargetsPath%\Platforms\x64'.

I had tried the same project/solution and it ran just fine in another computer that also had windows 7 64 bit, but a full version Visual Studio 2010 64 bit.

Now on this other computer, I'm trying to run the same program with Visual C++ 2010 express but get that error. What's more, my solution is, by default set on the configuration manager to x64, not win32. However, I can't open the project properties unless it's set to win32, otherwise it says "unknown error" on a pop up error message. Any idea is to be done? Anything I could add?

Correction: I am not even entire sure what this Visual C++ express 2010 version is. I thought it was x64 but I went back to the page I got it from (Visual C++ 2010 Express | Microsoft Visual Studio) and it doesn't specify, just says it's available for both...

The 64-bit compiler is an optional component. If you did not deliberately install it, it ain't there.

Of course! I just double checked and that was the difference. The full version of Visual Studio 2010 does have the 64 bit compiler. VC++ express only comes with x86. Thanks!

you can download the platform SDK for x64 from microsoft.