how do i know if my mac works with 32 or 64 bit of windows 7

See > http://support.apple.com/kb/HT1846 This site will tell you if you can install a 32 or 64-bit Windows version on the computer. In most of the cases, you can install the version you want but in other cases, you have to install the 32-bit edition (on old computers) or only the 64-bit version (on new computers)