As a System Admin i get the above error from time to time in my company... here are some Tried and Tested methods
First Try this free tool called
Remove Restrictions Tool (RRT) which is able to re-enables all what the virus had previously disabled, and gives you back the control over your own computer.
Get it from here
Remove Restrictions Tool is able to re-enable:
- Registry Tools (regedit)
- Ctrl+Alt+Del
- Folder Options
- Show Hidden Files
Small and easy to use. Make sure you boot in to Safe Mode to use Remove Restrictions Tool (RRT). Just click on the buttons and it’ll do it’s job.
ELSE
Try the following links
In Case you get the same error with Task Manager try following
Method 1
Click Start, Run and type this command exactly as given below: (better - Copy and paste)
REG add HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System /v DisableTaskMgr /t REG_DWORD /d 0 /f
Method 2
Download and run this REG fix and double-click it.
Method 3
• Click Start, Run and type Regedit.exe
• Navigate to the following branch:
HKEY_CURRENT_USER \ Software \ Microsoft \ Windows \ CurrentVersion \ Policies\ System
• In the right-pane, delete the value named DisableTaskMgr
• Close Regedit.exe
Method 4:
Using Group Policy Editor - for Windows XP Professional
• 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.
Hope it helps!!