HELP task manager d

  Hi,
I just got sent a program by someone over msn they tricked into thinking it
was something usefull when actualy the program disabled the task manger on my
account although set as computer adminstrator i tried running taskmgr.exe but
it looks like it has been set as a system policy becuase when running that it
says "Task manager has been disabled by your system administrator" i dont how
i can fix it? have you got any ideas? your help would greatly be appreciated!
Thanks,
Alex

Please help if you can