|you'll have to buy one. Unfortunately you should have accessed the hidden partition.|
Edit: check the sticker on your tower and see if it is XP home or XP pro, if it says XP media center then it will be XP Pro.
Borrow an XP Pro CD from family or friends (with the activation Key) and use that to re-install XP. When you activate it you can change it to the key on the sticker, that should work for you. You may have to call M$ when activating.
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