|Win XP is set by default to automatically Restart when it encounters an unrecoverable error.|
To have XP possibly display an error message you can investigate instead of the computer rebooting:
1. Click Start, and then right-click My Computer.
2. Click Properties.
3. Click the Advanced tab, and then click Settings under Startup and Recovery.
4. Under System failure, click on the small box beside Automatically restart to remove the checkmark.
5. Click OK, and then click OK.
If you then get an error message, look at all of it's details.
If a blue screen appears it will stay on the screen.
Copy down the things that are unique in the message and post them here.
STOP: 0Xx00000xx (we don't need the stuff in brackets beside that)
There may be a problem file named at the end of the text.
There may be a link to More info or similar - if so, click on it to see if it names a problem file.
There may be a mention of a MINIDUMP file having been made. That MINIDUMP file can be analyzed.