no Run, no shutdown on start

My computer is not right since last night! There is no Run, no shutdown (there is a logoff)on start. when try to oen task manager(ctrl alt DEl) and get the message "Task Manager has been disabled by your administrator".

But I am the administrator and did not disable task manager.
I did try to use the system restore function, but it says it can not restore it, there is no change made.

My Computer info: p4 2.8Mhz, win xp pro sp2, nortorn anti virus.

Any help will be apprecaited.