How do I re-enable a blocked task manager for Windows XP home edition?

Hello, recently my computer was hit by a very nasty trojan and a lot of my settings were messed with. Well I managed to clean all the junk out of my comp and kill all the trojans and their associated programs. Still I have one more problem, one of the trojans has blocked my task manager before it was destroyed and I have no idea how to re-enable it. Every time I use Ctrl-Alt-Del I get a message saying “Task manager has been disabled by my administrator”. If anyone could share some advice about what to do it would be much appreciated.