If you've reinstalled Windows XP while it was connected to the internet, reinstall it without any connection to the internet. It's been proven that a fresh XP machine (I believe pre-SP2) that has an internet connection can easily catch drive-by malware. However I'm certain this only applies if XP is directly connected to the internet, as opposed to going through a router. But this is just a precaution. Do not connect the network until you've installed XP to SP3 and enabled the Firewall. For additional safety nets, install some kind of malware protection like Malwarebyte's Anti-Malware
or Microsoft Security Essentials.
Go to http://download.cnet.com/Windows-XP-Ser ... 47919.html
to download SP1, put that on a thumb drive.