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.

Enabling Registry Editor *Administrative access to PC required

From a command prompt click START | RUN and in the run box type CMD and press Enter.
Copy the following codes
REG DELETE HKLM\Software\Microsoft\Windows\CurrentVersion\Policies\System /v DisableRegistryTools
If the above code fails then try
REG DELETE HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System /v DisableRegistryTools

if you don’t know how to copy in DOS then just copy those above codes in RUN command and go….