Hi there CN22, long time no see.............hope you are keeping well

Apart from the advice given above, there is one thing I would like you to try:

Swap out the RAM for a known good stick or at least run either the Microsoft Memory Test or MemTest86.

0x00000A37 is a very unusual stop error code in my experience, so I think that it might be a fundamental problem that you have. 512Mb is not a lot of RAM, and you can be sure that XP in normal mode will be using pretty much all of it within a few seconds of loading. That could be when it hits the bad areas and crashes.

The only other thing I think might vaguely be responsible is a corrupt user profile. I have known those produce some very strange error messages

Try creating a new one and see if that produces the same errors.

Cheers