That's a very common problem for Windows users. Many times when you try to open Task Manager, you find that "Task Manager" option has been grayed out:

Also when you try to run it by typing "taskmgr" in RUN dialog box, Windows shows following error message:
Task Manager has been disabled by your administrator.

There might be 2 possible reasons behind this problem:
- Your system administrator applied the restriction using Registry Editor or Group Policy Editor.
- Your system has been infected with virus and it has disabled the Task Manager.
If you are already the Administrator of the system, then your system is most probably infected. You should follow the instructions given in following topic first:
Is Your System Infected with a Virus / Spyware / Adware / Trojan?
Now if your system in not infected or you have successfully removed the virus, then you can follow these simple steps to enable Task Manager again:
1. Type regedit in RUN dialog box or Startmenu Search box and press Enter. It'll open Registry Editor. If Registry editor is also disabled, then follow instructions given in following tutorial:
How to Enable Tools -> Folder Options and Registry Editor in Windows
2. Now go to following keys one by one:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\System
HKEY_USERS\.default\Software\Microsoft\Windows\CurrentVersion\Policies\System
and look for a DWORD value "DisableTaskMgr" in right-side pane. If you find it, delete it.

3. That's it. Now Task Manager will be enabled.
PS: If you are not familiar with editing the registry, then you can use ready-made registry script to do the task automatically. Download following ZIP file, extract it and then run the extracted .REG file. It'll ask for confirmation, accept it:
This article was posted by VG in following section: Troubleshooting, Windows 7, Windows Vista, Windows XP.
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auah
thx, this information really helpful for me. :D
anil
Thanks its working.
thank you so much...
Ak
I use symantec endpoint protection in vista and it shows that live update has been disabled how to enable it???
chaplin
PROBLEM SOLVED WITH NORTON the FREE 30 days Trial !
I had same problem and I did try what all the sites said about it, but didn't work. I HAD A VIRUS !
Then I tried the norton antivirus free trial for 30 day, I did a scan and found out this :
Resolved Threats:
W32.Sality.AE
Type: Anomaly
Risk: High (High Stealth, High Removal, High Performance, High Privacy)
Categories: Virus
now I can use task manager and I have to reinstall winamp and some other software because the exe files of them were infected. Also norton did repair some software that i had on my PC ( laptop ) but not installed, obviously the virus did infect them as well.
my advice is : do a scan with norton the free version trial for 30 days and get rid of the virus today, because in a few days he will infect almost everything.
so , the name of this virus is SALITY . AE
PS - now I have to delete the norton because it makes bips every few seconds and I cannot find in settings anything that allows me to turn off the audio signal.
Calleat
yo u are really really really really really really really really really really really AWESOME dude, u have save my computer and i am really thank ful. u're the best and thanks.
visit my web and do anything u like :) X10000 :D x9999999999
Majed
thaaaaaaaaaaaaaaaaaaaank yoooooooooooooooooooooou very much :))))
chaplin
Glad I could help :) Great ! The bip was not from Norton, but from something that the virus left. I did delete it after searching all topics that I could find about "annoying beeping "
Sality AE is a virus that collects passwords and accounts from any PC it can infect and send the data to some hacker :) Maybe saving your card info, passwords on the pc is not a good ideea :) Thanks for the Norton, the only antivirus that did clean my laptop. even I don't like norton because it slows down my speed...Great. All the stuff that is written in the first 5 pages here didn't work for me, that's why I thought I should post what DID WORK :) Cheers !
vin
the "regedit.exe" command & "taskmgr" are disable the virus so help me......
it's trick are not worked........
chaplin
doesn't work with any of the suggestion on all 6 pages mentioned; only this , as I 've posted a few month ago:
PROBLEM SOLVED WITH NORTON the FREE 30 days Trial !
I had same problem and I did try what all the sites said about it, but didn't work. I HAD A VIRUS !
Then I tried the norton antivirus free trial for 30 day, I did a scan and found out this :
Resolved Threats:
W32.Sality.AE
Type: Anomaly
Risk: High (High Stealth, High Removal, High Performance, High Privacy)
Categories: Virus
Uewd
I have a question, If the task manager has been disabled by a virus and I want to terminate it, can I use 3rd party software (like TuneUp Process Manager) to do this?