Need to lockdown/protect computer

[setspeed]

Hi there, i need some advice about securing my computer against a novice girlfriend who will be using it regularly from now on.
Im running XP behind a router with a hardware firewall, however i want to ensure that she cant download any nasties/trojans, install any programs or generally change anything at all.
I need to achieve this while still allowing her to download certain types of files (mp3, avi, etc) and still do her girly stuff on the net, facebook, windows messenger etc. Im forcing her to run in a non-admin account and use firefox, also have winpatrol installed along with avg antivirus, and using spybot hosts list.
Any suggestions as to some free software, or settings i ought to change within windows to avoid my computer getting rooted. I would try to educate her, but dont have the time!

[Unbanable]

XP Home or Pro?

[setspeed]

Originally Posted by Unbanable

XP Home or Pro?

XP Home.