A virus is a common problem on the PC, from hiding files to remove the file.
in addition to destroying files, the virus can also damage the system files on the windows, one of whom is disabled TASK MANAGER and REGEDIT.
Some ways to fix the file system are:

A. ACTIVATE “REGEDIT”
1. Click start menu and select “Run”
2. Enter “gpedit.msc”
3. Then select the “User configuration”
4. Select the “Administrative templates”
5. Select “system”
6. Double click “Prevent access to registry editing tools”
7. On the tab “settings” select “disable” -> REGEDIT problems completed

B. ACTIVATE “TASK MANAGER”
1. Follow the steps above point 1 to point 5
2. Select “Ctrl + Alt + Dell Options”
3. Double click on “Remove Task Manager ”
4. On the settings tab select “Disable” -> complete TASK MANAGER problem

When I d above still can not,
1. Try to get into “SAFE MODE” dg how pressing the “F8″ at boot (enter boot selection menu) and select “SAFE MODE”
2. Usually before entering the “SAFE MODE” You are asked to choose the “Administrator or User (user name is usually the name of the owner of a computer), select” administrator ”
3. Once signed in “SAFE MODE” to do the steps above (points A and B)
4. Restart

Hope can help solve your problem ….
Good luck ….