[dragnet]

I have just purchased a second hand computer, it is running XP professional, however what I have since found out is it was being used on a network. The security centre has been completely removed. How do I replace the security centre? What other things should I look for that may have been changed by the network manager?
Also if I receive e-mails containing .gif files, some I can open and view others will not open. Anyone got any clues, any help would be appreciated.

[new tech guy]

If it is a new machine and was second hand, the best bet is probably just to bomb the hard drive with a windows disc and start fresh. Wouldnt trust it if another user has used it. Who knows if there are any infections, security issues, etc that could be there.