Task manager can be disabled manually, but more commonly it’s disabled by a virus. It’s easy to re-enable once you’re virus-free Leo Notenboom

My task manager has a "task manager has been disabled by the administrator" message. How did this happen and how can I correct this?
Why: if you didn’t do it yourself, the news isn’t good. How to fix it: there are a couple of ways. Let’s look at this more closely.

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Some time ago I received an email from a reader curious why their Task Manager option was grayed out on the taskbar right-click menu. After a bit of research his problem was solved, and now I’m sharing the solution with everybody.

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It is a versatile task management and system utility in Windows operating system. With Task Manager, user can view detailed information about computer performance (CPU usage, physical memory, kernel memory, handle, thread, commit charge, etc.), running applications, processes, network activity and statistics, logged-on users, and system services. Besides system information, The Manager can also be used to set process priorities, processor affinity, forcibly terminate processes, and shut down, restart, hibernate or log off from Windows.
In view of its powerful capabilities and functionality, administrator may want to disable it in the computer to disallow user from running the tool, although administrator also needs to restrict user access to Registry Editor or ability to change system registry for the control to be useful. On the other hand, some users may be wondering why the Task Manager has been disabled and cannot be run, which often caused by intelligent malware and Trojan to prevent users from terminating the malicious process. In any way, disable or enable Task Manager can be done by just a simple registry change.

How to disable Task Managaer read on My Digital Life

Sometimes one needs to disable the task manager to give clients limited access in a network or to prevent other users from doing a specific task. There are multiple software available for this purpose, but the best way is to disable it using Local Group Policy Editor which is build-in your Windows and does not require any software to be installed.
To begin with you will have to open Local Group Policy Editor, to do this go to Run and enter gpedit.msc.

Read more How To Disable Windows Task Manager Using Registry

To make manual inspection and removal more difficult, malware often disables access to Task Manager. Fortunately, a few quick Registry edits are usually all that are needed to regain control. Here’s how.

Read more How To Enable Task Manager | About.com

The following knowledgebase will help you to resolve the error message "Task Manager has been disabled by your administrator" when you try to use "Task Manager"

Read more "Task Manager has been disabled by your administrator" error message | Knowledgebase article

Let’s face it. All of us have been infected by virus before. Even if you have anti-virus installed, you can still be infected by a new or custom virus that is not recognized by your anti-virus. Sometimes after removing the virus completely from our system, you’ll face new problems such as you can no longer bring up Windows Task Manager from CTRL+ALT+DEL. You get the error message saying “Task Manager has been disabled by your administrator”.
You think that it’s easy to fix this problem by going to Registry Editor but you can’t! You get the error message “Registry editing has been disabled by your administrator“.

Read more Restore Task Manager, Regedit and Folder Options Disabled by Virus | Raymond.CC

We have received mails from some readers about task manager is disabled on their system suddenly. Problem: It is due to some kind of virus/ trojan activity which normally disables the task manager. Now due to this problem when ever the user press alt+ctrl+del to launch it, windows gives an error saying “Task Manager is being disabled by your administrator”.

To enable the tool on your system 1. Press window key+r to show run prompt 2. Follow the following steps

Read more about the problem in windows xp | Trouble Fixers

Tips & Warnings: back up your registry prior to making any major changes to the system. The easiest way to back up the registry is to use Windows XP’s system restore feature. It will save the registry as it was prior to the changes you make. Avoid ending processes that are running under the direction of the system, as opposed to those processes running for a particular user. System processes are enabled to help keep the computer running correctly. Closing such applications can cause errors or instability in Windows XP. Be very careful whenever you are editing the system registry. Syntax errors in the registry can cause serious errors to occur.

Read instruction (8 simple steps) | answerbag