spontaneous shut down

My computer spontaneously shuts down when I am using the
internet. An error comes up that the computer has
performed an illegal operation and must shut down. Then
it restarts automatically saying that the computer has
recovered from a serious error. Error causes by device
driver. I re-installed Windows XP but did not delete the
old copy. The computer manufacter believes that the old
copy might be the problem but told me to check w/
Microsoft. Please respond.