Given the scenario, you might find yourself not being able to access your task manager (local network policy, company policy, user access rights etc). And the thing is, sometimes, you just need to access it to kill an app, or to kill a process, or to check the computer’s performance etc.

As usual, before playing around with the registry, always back it up (guide here). But to be honest, this is just a minor edit, hence the risk factor is very low.
To quickly enable it, click start.
Click Run and paste the following command into the text field:
REG add HKCUSoftwareMicrosoftWindowsCurrentVersionPoliciesSystem /v DisableTaskMgr /t REG_DWORD /d 0 /f

Click OK. That’s it! That should solve your problem!