Compiling for 64 bit on a 32 bit machine

http://social.msdn.microsoft.com/Forums/en/netfx64bit/thread/f21450f5-b36d-4ea2-9806-f169aff0388d

Goto Add/Remove programs, select Visual Studio, Change, Add/Remove features and add x64 compilers from C++ node. After installing x64 compilers, you should see appropriate options under Platform and shoudl be able to build x64 projects on 32 bit machine.