Click on “Start” then on “Run” or alternatively you can press Windows Key and R to open ‘Run prompt’ or see “Run prompt” image.
Now type “gpedit.msc” without quotes in the textbox and hit Enter key. This should open ‘Group Policy Editor’.
Now follow to: User Configuration -> Administrative Templates -> System-> Ctrl+Alt+Del Options or see image of “Group Policy of Task Manager”.
Now on right side pane you will find “Remove Task Manager”, double click it. It will open “Remove Task Manager properties”.
Now select “Disabled” radio button and click Apply and OK and you Task Manger is enabled or see image “Remove Task Manager properties”.
This is how you can enable task manager disabled by virus or any malware. If for any reason you cannot access Group Policy Editor’ (XP home does not have Group Policy Editor’) then you can try alternate method. Press Windows key + R and copy paste following lines in the textbox without quotes and hit Enter key.
“REG add HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System /v DisableRegistryTools /t REG_DWORD /d 0 /f”
Now you can open Task Manager but if cannot open then restart your PC and then try to open Task Manager. Still you have any problem then drop comment with Operating System name. I’ll try my best to solve your problem. [Via]