Computer step by step
 Make your Pc better
Type C:\Windows\System32 and press ok
In the System32 folder you can find taskmgr file
Disable:          
When you try to open Task Manager from Start bar the button is grayed out
When you try to open Task Manager this message will be displayed:
Task Manager has been disable by your administrator.
Gpedit:          

Warning Computers running Windows 7 Home do not have access to Group Policy (gpedit.msc)
This method shows you how to Disable/Enable Task Manager from Group Policy
Please perform the following steps:

Please go to Pearl button (Start) and click on the Search programs and files
For more information about the change from Start to Pearl button click here
Type gpedit.msc and press Enter
In the Group Policy window please navigate to User Configuration -> Administrative Templates ->
System -> Ctrl+Alt+Del Options  and open Remove Task Manager
The Default state is Not Configured and Task Manager is Enable
To Enable taskmgr select Disable
To Disable taskmgr select Enable

To finish press ok button and close Group Policy window
Type cmd, right click on cmd icon under the Programs and click on Run as administrator
Please confirm User Account Control pop-up
Please select, right and copy a registry key from below, then right click on command prompt window
, select Paste and press Enter

To Disable Task Manager:

REG add HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System /v DisableTaskMgr /t REG_DWORD /d 1 /f

To Enable Task Manager:

REG add HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System /v DisableTaskMgr /t REG_DWORD /d 0 /f

To finish please close command prompt window
Regedit:   
This method shows you how to Disable/Enable Task Manager from Registry Editor
Please perform the following steps:

Please go to Pearl button (Start) and click on the Search programs and files
For more information about the change from Start to Pearl button click here
Type regedit and press ok
Please confirm UAC pop-ups in order to continue
Microsoft official disclaimer

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by
using another method. These problems might require that you reinstall the operating system. Microsoft
cannot guarantee that these problems can be solved. Modify the registry at your own risk.

Please navigate to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies
\System and locate DisableTaskMgr registrykey
Double click on DisableTaskMgr and edit the value:

To Disable Task Manager:

Change the data value with 1

To Enable Task Manager:

Change the data value with 0

To finish press ok button and close Registry Editor window
Path:          
This method shows you where Task Manager is located in Windows using Windows Explorer
Please perform the following steps:

Please go to Pearl button (Start) and click on the Search programs and files
For more information about the change from Start to Pearl button click here
Description:  

Task Manager provides information about applications currently running on your system, the processes
and memory usage or other data about those processes, and statistics about memory and processor
performance.

For more information please continue to read the official Microsoft article
How to Disable/Enable Task Manager
Windows Vista Windows 7 Windows Xp
CMD:   
This method shows you how to Disable/Enable Task Manager from Command Prompt
Please perform the following steps:

Please go to Pearl button (Start) and click on the Search programs and files
For more information about the change from Start to Pearl button click here
   
   
   
   
   
   
Description Path Disable Gpedit Back CMD Regedit Up Back