Whenever you ask about Windows XP, it's important to state what version
of XP you have, including the service pack.
When asking about a problem, it's better if you can offer any clues
about why you may be experiencing the problem, e.g., recent changes to
software or hardware. The fewer details you provide, the more generic
your answers will be.
If you can do the following procedure in Safe Mode it will be easier.
In Safe Mode or in 'normal' mode: Control Panel > System > Advanced tab
Startup and Recovery Settings button > Advanced tab > remove the
check mark from 'Automatically restart.'
Now restart your computer. When your computer freezes at a blue screen,
read the message. At the bottom of the message, copy the number (it
begins with 0x000...) and the name of the error (LOOKS_LIKE_THIS.)
Post again with your complete version of Windows, any clues you might
have to explain your problem, and the number and name of the error you saw.