You posted while I was typing
Explorer and my computer use both Explorer.exe. the problem might be in one the the applets Explorer is loading. The difference is just the skin of the program. You can even make the My Computer navigator look like Explorer if you to to Folder options
I recomend you to reinstall XP because you have a lot of RAM. Just as a detail, not that this produces the crash, but do you know the maximun RAM for your motherboard? If you pass it, it will decrease performance instead of expand it. I guess with 396 MB tyou have 1 128MB and 1 256 MB.
Some Mobos, don't support more than 380, and others no more than 512 MB Just a suggestion