How to restore to factory settings

Hello,
i can't seem to do anything. i've tried pressing F8 repeatedly, but it doesn't bring up anything that says "repair my computer" i have anti virus software, but i loaded it after i already had a virus which wouldn't let me install all of it. i have a toshiba satellite, but it's just really confusing. it happened last night and i have already backed up all my things on an external drive, but i just don't know how to restore it to factory settings and i don't have a backup disk. i just didn't know if there was anyway to make it back to the way it was when i first got it. I'm trying to do some things in safe mode right now, but i'm pretty much clueless. my McAfee is trying to repair itself, but it can't for some reason. and yes i have my networking on.

thanks.