|Make sure you have an XP installation disc and then I would suggest using DBAN:|
Use that and let it automatically check and nuke your HD. That will make sure that there is no virus whatsoever on the HD.
Then use your disc and do a fresh reformat and install of XP.
Then do all your critical updates, check the device managers for any errors and if there are any conflicts, go to the laptop website and download the new drivers.
That should get you going.
You will need an antivirus, I would suggest Avast Free:
Microsoft Security Essentials:
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