Not necessarily, but SP2 is no longer supported, in fact, you haven't been receiving critical updates since July of last year!
You mentioned your firewall software, what about anti-virus and anti-malware?
You say you've reformatted, but have you scanned applications that you have saved before running them on your freshly installed OS?
Install XP on a fully (quick will do) formatted drive with no network capabilities (no network cable/wireless card attached) --> install latest service pack (SP3 here) while still offline --> install AV/AW/FW while still offline --> connect to the internet to download latest Microsoft critical updates, AV/AW definitions.
There is a program I use called CTUpdate
that will allow you to download MS updates for various products, including Office. You can then run these updates while offline. This is your best bet if you have a safe/clean computer that you can use to download the files to, then burn to disc, put on an external drive, etc...