Windows 32-bit vs 64-bit wouldn't cause random crashes and it doesn't sound like he's out of RAM...

What kind of crashes are these? It happens after playing for a while? Without having any information about the crash it's kind of hard to even guess what's happening. For example, if it's a WoW #132 crash, then the answer would be to run the WoW repair tool. If you get a Lavish Crash Reporter box, then it would help to send the error report, and you can also try running the development build of Inner Space -- to do so, right click the IS icon in the system tray, select Patcher, check "Download development (test) patches", then close and restart IS