after installing windows xp home. my internet sessions now
are no longer than about 1 min. get error message saying
that windows will now shut down, followed by the following:
NT AUTHORITY/SYSTEM. it gives a min to close all
programmes and then restarts windows. this happens every
time i try to log onto internet. i am using btyahoo?

Its called Blaster worm virus. Get youself an up to date virus killer.