Why i can't use my Task Manager function?

I'm using Windows XP Profesional. My system has been affected by virus but my antivirus has killed it. After that incident, i can't use my task manager function.When i press ctrl+alt+del it said that task manager has been disabled by administrator. I also can't use Folder Option function. I can't find it after that virus incident.What should i do to get this two function back?Anyone please hel me.Thanks for advance.