I've had several machines show this message 0x50 BSOD error in Windows XP Service Pack 2. In all the cases where I saw this message the computer boots back up on the next cold boot. For the error not to reoccur follow the steps in the KB Article:
What worked for me:
I started out by updating the Video adapter and then the BIOS update and then running the chkdsk utility. For detailed instructions on how to run chkdsk and different parameters... click this link... If the error re-occurs after a few days or so, the best option is to run one of many free RAM tests available on the Internet. You can also download one from Microsoft's website
If the test fails YES, it is time to replace the memory.