One way is you can go to the Control Panel - System. If it says 64 bit like in the pic, you have 64 bit Windows installed. If it doesn't say that, then you have the 32 bit installed.
You can get basic specs laid out simple from something like speccy.
Speccy - System Information - Free Download
Have you tried downloading and installing the newest version of iTunes yet?
iTunes 9.2.1 Released