Ok, let's try
memtest86, not because I think the ram is bad (since you just replaced it), but I wan't to know if there might be an issue with the motherboards memory slot/s. If that comes out clean, try doing a clean boot of XP. There may be some software your running that is causing these errors.
How to clean boot XP
I'm assuming you're still getting BSOD's, next time it happens, can you post the error, the file involved (if it's listed) and the stop code?