Login related problem in computer

What doesn't work? Re-installing Windows? Why not?

The logon issue is not too hard to fix, need to set the logon program back to the default one. You need either a second PC on the network or a boot disk that has registry edit software like Bart PE.

Log on to a networked computer.
Run Regedit.exe
Point your cursor to HKEY_LOCAL_MACHINE
Select File > Connect Remote Registry
Type computer name (infected computer)
Navigate to the following location in registry of destination or infected computer


HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon


Edit these two values in right pane:

Shell
Userinit


Change these two values to
Shell=explorer.exe
Userinit = x:\windows\system32\userinit.exe
Exit from Registry
Restart Infected computer.
You should be able to log on to computer.
if it not work then go to back steps and just copy orwrite the file userinit.exe