Perhaps look through your CDs that came with the PC. See if there's an MS Office CD or a backup CD. Save all your data very carefully, then run the backup CD and see what the options are.
Contact the PC vendor and ask for documentation on the Office suite. If it is all legit then probably the install is an OEM one, meaning that your contract is with the PC dealer not MS. So the dealer needs to sort it out or give you advice.
Probably it's out of warranty though so perhaps you could speak to them nicely and ask what they suggest.
Also see if there is a forum for owners of that PC / laptop, and/or for customers of that dealer.
The outlook isn't good but there may be a way to get out from under, depending on how much time you're willing to put into fixing it. In the meantime, if you install OpenOffice as MC has suggested, it does handle all those files, so you could carry on working. You might decide that you are happy to say goodbye to Mr Gates's product after that, you never know.
It depends on the cost v aggravation issue no doubt. See what the cost of a new MS Office suite is
