Task Manager has been disabled by your administrator
I have been working on more and more computers where this error has been more frequent. If you get this error, it is highly likely your computer has been infected with a Virus or Malware. You first should download or open your favorite Virus / Malware program, update the virus or definition files, and run a complete scan. These viruses will place this restriction on your system so you cannot “End Task” them. There are several methods you can use to re-enable your Task Manager and eliminate the error “Task Manager has been disabled by your administrator”. The following fixes are listed from easiest to hardest.

Download - Enable_Task_Manager_Registry.zip
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REG add HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System /v DisableTaskMgr /t REG_DWORD /d 0 /f
HKEY_CURRENT_USER \ Software \ Microsoft \ Windows \ CurrentVersion \ Policies\ System
This is the registry fix for computers in which the .txt or TXT file association has been removed. The end result is when you attempt to open a Text Document or .txt file, the Open With Dialog box will appear and you will not be able to open these files using windows. TXT Files Will Not Load You could go into your Windows Registry and edit it, which I highly discourage. You can download the file below and extract the file, and double click on the .reg (registry) file. You will get an “Are you sure dialog box”. Click yes and this should fix your problem.
Windows XP TXT Registry Fix (798 Bytes, 10 hits)
This is the registry fix for computers in which the .zip or ZIP file association has been removed. The end result is when you attempt to open a Zip Archive or .zip file, the Open With Dialog box will appear and you will not be able to open these files using windows. ZIP Files Will Not Load You could go into your Windows Registry and edit it, which I highly discourage. You can download the below and double click on the file. You will get an “Are you sure dialog box”. Click yes and this should fix your problem.
Windows XP ZIP Registry Fix (6.0 KB, 783 hits)
Recently, I have been fixing a lot of computers where a Virus has attacked a computer and Removed the .exe file association. The end result is when you attempt to open an executable file .exe file, the Open With Dialog box will appear every time and you will not be able to open these files. Executable Files Will Not Load You could go into your Windows Registry and edit it, which I highly discourage. You can download the below file, unzip it, and double click on the file. You will get an “Are you sure dialog box”. Click yes and this should fix your problem.
Download - xp_exe_reg_fix.zip
Downloaded 3317 times Password: mkwebdesign