I have two sets of program files when I don't have a 64 bit system.

[Petie]

I don't know what your brother did for sure but it sounds like he copied the hard drive, not just your user folder, when backing up your files. While annoying, the best course of action in this case would be to back up the files you need (documents, pictures, music, videos, etc.), wipe the hard drive, and reinstall with a 64-bit edition of Windows because you're wasting resources running a 32-bit OS.