Enable the Taskmanager...

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

• 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 3:  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.

Method 4: Change Task Manager through a Registry REG file

1. Click on Start, Run, and type Notepad and press Enter
2. Copy and paste the information between the dotted lines into Notepad and save it to your desktop as taskmanager.reg

------------------------------------
Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System]
"DisableTaskMgr"=dword:00000000
-------------------------------------

      3. Double click on the taskmanager.reg file to enter the information into the Windows registry