I am currently running Windows XP Professional on my computer. My configuration is Intel Dual Core 3.00 GHz, 512 MB RAM, 160 GB HDD. Sometimes, the computer just restarts without any particular reason. After restarting, I get an error report, "Windows has just recovered from a serious error." Such incidents happen once in 5-6 days. I don't face any other problems apart from this. Also, I don't face this problem in Ubuntu Karmic Koala though.
In Windows Event Viewer sometimes the standard blue "For more information"-link, in fact brings you to a very specific knowledge base article:
(Do not click it here; when clicked from Event Viewer, the above link might include the event ID and maybe even more. If the Event Viewer gives you any other information, then add those to your question please.)
So: if there's anything in Event Viewer, then maybe you can get more information by clicking that link.
(For screen captures see also How To Solve Any Windows Problem with Event ID.)
First, see if anything interesting is to be found in the Error Log.
In most cases the problem is hardware overheating. When the problem occurs, you might open the case and see if the RAM or GPU are too hot. If they are, first step is to clean well inside the case and especially all air conduits.
You might also check that the RAM and all cards are well-sited : Take them out, clean the contacts and resit.