Often the action of viruses (at least - reckless actions of users) lead to the fact that the Windows Task Manager is blocked, not responding to attempts to cause.
Few people want to reinstall because of this whole system, but to do this and do not need - how to return the Task Manager are available.
The best way to install to replace the standard Windows Task Manager is blocked more advanced functionality of the program Process Explorer ( http://technet.microsoft.com/ru-ru/sysinternals/bb896653 ) Having significantly enhanced functionality.
If you want to return to it originalTask Manager, or the installation of another does not help, try using the Windows Registry Editor to check the key [HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionPoliciesSystem] and if there DisableTaskMgr entry with a value of 1, delete it.
You can enable the Task Manager through the toolControl Group Policy (gpedit.msc). There, in the "Opportunities Ctrl + Alt + Del» section, locate the "Remove Task Manager" and set it to "off".