I currently run XP on every machine we have and use the following:
Anti Virus: Microsoft Security Essentials
Firewall: Windows XP's
Cleaning, Uninstalls & Registry Tweaks: CCleaner
Defragmentation: Defraggler
File Recovery: Recuva
Spyware Protection: SUPERAntiSpyware
Malware Protection: Malwarebytes Anti Malware Free
Back Up: Microsoft SyncToy
All of which are my favourite software price, free!