If you are getting error, "Task Manager has been disabled by your administrator" , when trying to launch task manger on Windows XP machine then here is a simple solution for you.
Solution: Click “Start >> Run” and type following command exactly as given below and click OK.
REG add HKCUSoftwareMicrosoftWindowsCurrentVersionPoliciesSystem /v DisableTaskMgr /t REG_DWORD /d 0 /f
Yep. This problem is solved now! In case you any other problem feel free to ask.