Before doing anything, e.g. formating, installing & anything else try if possible to download spybot & any decent firewall and anti-virus, and place on a USB Memory Stick.
Installation:-
1)Format Hard Drive,
2)Install Windows,
3)Install Firewall + Anti-Virus,
4)Install Spybot
5)Make a backup of your registry with spybot
6)Update Spybot + Firewall + Anti-Virus
7)Download Firefox
---
If all else fails just install linux ^^
