Windows repair install gone bad

I am doing a repair install on a windows xp home machine but used a xp pro install full version cd by mistake. I have a key code for xp pro full that I havent sold yet and used that to try and complete the upgrade planning to uninstall the upgrade after it finishes the start over with the correct xp home disk. Seemed like a good plan until windows refuses to take the key code on the COA sticker. Anyone know a way to cancel the upgrade? Choosing to boot to last know conifiguration that worked is useless as it goes back to the xp pro upgrade. HELP!!

Give the following a try.

1. Restart your computer.
2. Start pressing the F8 key.
3. On the Advanced Options menu, select Return to OS Choices Menu and press Enter.
4. Select the Cancel Windows XP Setup option.

Hope this work. If not let me know and will find another solution.