Activation issue - XP Home

I originally had a problem with DEP errors (thread http://forums.majorgeeks.com/showthread.php?t=158642) so I tried a repair install. Now Windows lods to the login screen, I'll select a user (there's only two) and when I do it says I have to activate. Fine. So I'll click 'Yes, let's activate now' and the window closes then it goes right into the 'logging off' routine and goes back to the login screen. It doesn't even try to activate, nor do I get asked if I want to activate over internet or telephone or anything. I just click Yes to activate and it logs off back to the user list/login screen.

Any ideas?

Thanks!