I'll add a bit to BlueWizard's suggestion.
A USB drive is just a small hard drive that you plug into a USB port. It's essentially a gigantic floppy disk - you can drag and drop files onto it. And given it's a holiday weekend sort of thing, there's sales all over the place. You could snag a 1 gig drive for 30 or so if you shop around, and a 2 gig for 50-60. Then it's just a question of navigating to the folders you have stuff in, and copying/pasting onto the USB drive. Generally you don't need to install any drivers or anything like that, so this is honestly the best way to go.
If you need more space than that, then you can burn files to CDs. You'd need a program like Nero or EZCD Creator to do that, or you can get a free one like Burnatonce (
http://www.burnatonce.net/downloads/) or CDBurnerPro XP (
http://www.snapfiles.com/get/cdburnerxp.html). Keep in mind these are free programs and as such as a little slower and less featured than something you'd buy. Otherwise, you
can do it natively in Windows XP if that's the OS you are running, but I don't suggest this because it's a pretty weak burning mechanism - you'd do better to get a freebie.
To reformat/reinstall (after you've backed up your files), you'd pop a Windows CD into your computer and reboot. It
should detect that you have a boot CD in your drive, and will say something like "Press any key to boot from CD." You'll hit a button and it will go into the Windows startup screens - they are blue and look like old DOS shells. You'll follow the instructions to reformat/reinstall - so you'll do things like if you want to delete partitions (which you do, as it will wipe out any viruses probably on your machine), and select which partition to install XP to. The commands are simple - I think it's like D to delete, L for a full delete, etc. Just follow the instructions and you'll be fine.
'Course, keep in mind that when you do that, you'll kill everything on your hard drive. If you've got games and programs, you'll need to reinstall them. If there's anything with saved games (for example, Warcraft III) you'll have to manually back those sorts of files up. Also, it would be a good idea to copy down your e-mail settings if you're using something like Outlook - so your account information, SMTP/POP3 servers, etc. (That can all be found in Options -> Accounts). Also, if there's any pictures, music, or chat logs you want to save, get them as well.
Finally, when you get back up, install some of those programs I linked to earlier - Avast, Windows Defender, etc. It would help you immensly if you were to download them now, save them to a CD or USB drive, and then install them immediately after you reformat and reinstall Windows. I'd go as far to suggest that you disconnect from the Internet entirely until you've gotten antivirus installed.
Anyway, let us know if this works out or if you need anymore help.
Good luck!