well... theres no way to format your C:\ without getting rid of your OS and your microsoft apps. If you don't have the disks then you're pretty much out of luck there.
Here's some stuff you can do.
-- download SpyBot Search and Destroy HERE ---->
LINK --- its free, even though he asks for you to donate. Download the latest protection uipdates and let the sucker scan. When it's done, click "fix selected problems"
-- download the latest security updates for your version of NAV (norton anti virus) at the symantec website. It isn't hard to find. Make sure that you download the correct updates for your version of the software. Download it to your desktop, then double click on it to deploy it to your current version of NAV.
-- Disable system restore, and you can do this by clicking "Start >> all programs>> Accessories >> System tools>> system restore" Once you're in that menu, click on 'system restore settings' and check the checkbox that says "turn off system restore" click yes, when it asks you if you're sure, and then ok.
-- Restart the computer in safe mode... you know how to do that? Press F8 repeatedly when its booting up until it gives you the option to boot up into safe mode. When you're in safe mode, run a full system scan on your updated NAV.
-- While in safe mode, it may not hurt to run SpyBot again.
-- Run a chkdsk. Start >> Run>> chkdsk /f
Um... yeah... thats pretty much it.
Your other option is to acquire the disks for Windows XP and Microsoft Office. They aren't too hard to come by.... then formatting the whole thing. However... since you don't have that... try what I put up.