Windows shuts down when i go online with the following message
initiated by NT AUTHORITY/ SYSTEM

reason
RPC terminated unexpectedly

OS:

WIN XP PRO version 2002

there is no mention of service packs

Sounds like you have the Sasser Worm, please click HERE for removal instructions. If you see a message like the one I have attached you are infected.

you just (if yu see the message in the image above) go start>run> and type shutdown -a
to stop it.

it doesn't prevent it permanently though.