Sorry to hear that you're having difficulties. The solution is pretty simple, and you probably don't want to complicate it further by installing Windows XP Home or a new copy of XP Pro on your Tablet PC. When you call HP technical support and they should provide you with a recovery CD for the operating system. The TC1000 is out of warranty, so there may be a fee.
Here is HP's technical support page for the TC1000:
Compaq tc1000 Tablet PC*-* Contact HP - HP Business Support Center