Task Manager Disabled:

Using Group Policy Editor - for Windows XP Professional to Enable Task Manager.

* Click Start, Run, type gpedit.msc and click OK.
* Navigate to this branch:

User Configuration / Administrative Templates / System / Ctrl+Alt+Delete Options / Remove Task Manager

* Double-click the Remove Task Manager option.
* Set the policy to Not Configured.

Enable RegEdit [It is not tested]

REGEDIT4
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersio
n\Policies\System]
"DisableRegistryTools"=dword:00000000

Save the text file as any name u with extension .reg
example:- "enable.reg"
After that double click to run the file.

Note:DO SCAN YOUR MACHINE WITH A GOOD ANTIVIRUS. BECAUSE THIS PROGRAMS DON'T TURNED OFF BY HIMSELF OR AUTOMATICALLY. IT HAS TO A VIRUS EFFECT OR A ADMINISTRATOR HAS TO MANUALLY DISABLE THIS PROGRAMS.