Many of the computer users have faced this problem. Keyboard is not working!! At first check the cable connection. If that is ok then most probably there are virus which is responsible for this. Trojan horse (Trojan.Win32.VB.dsu) is the virus which do that. It usually remain as acdsee.exe and inactivate the keyboard. So to get rid of this you have to install the OS again!! No , no need of that. You can get rid of this by editing the registry. But problem is that as the virus open just after opening of OS . so if you edit the registry in conventional way, that will remain like before and problem will not be solved. So you have to edit that before log in. How? Here is the way. May be complicated. But it is tested and worked.
At first after log in go to: C:\WINDOWS\system32 (it OS is installed in C drive). Than search the file named sethc.exe and make a back up of it. or you can rename it or copy and paste it in another folder. Now search the file named cmd.exe, make a copy of it in another folder or in desktop, rename it with the name of sethc.exe and paste it in system32 folder. Actually overwrite it.
Then log off( not shut down) your pc and hit Shift 5times repeatedly. Command window will be opened and write regedit.exe in command prompt and hit enter. Registry editor will be opened.
Now go to: HKEY_CURRENT_USER\Software\Microsoft\Windows\ShellNoRoam\MUICache. Here you have to remove value of the string named C:\Windows\help\services.exe
Then go to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon , double click on the string value named Shell. Now remove the rest of information on the right side leaving “Explorer.exe” in the value date. Now close the editor.
Now after log in , your keyboard will work. At last re-paste back file of sethc.exe in system32(actually overwrite).