What kind of symbols?? Foreign language maybe?? It could be possible that something hacked your registry and your language preference has been altered. Other than that....these wackos out there doing viruses, worms, trojans etc... are always a step ahead of the antivirus folks. Sucks!!!!
That's why I have my OS on it's own partition....reinstall/repair no problem.
Hey that's a thought...have you tried the repair function in Win XP or the restore function???