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This issue is most likely caused by the virus modifying the shell or userinit values in the registry.
The first thing worth trying is go into the safe mode and choose to do a System Restore. Then restore your PC to a point prior to when you downloaded the infected file.
If you cannot get system restore to run, another option would be to boot your Windows disc and run a repair.
If you really do not want to go through a Windows repair process and feel confident in trying some advanced steps, you can try using a BartPE boot disc from your PC’s operating system disc (assuming you’re using Windows XP). You can get steps on how to build a BartPE CD here.
Once you have created the BartPE CD, boot it (select ‘No’ if it asks to enable networking), then perform the following:
[li]Go into the start menu, click ‘Run’, type in ‘regedit’ and click ‘OK’.[/li][li]Click on “HKEY_LOCAL_MACHINE”, then go into the File menu and select “Load Hive”[/li][li]In the file name field, type in “c:\windows\system32\config\software” and click ‘Open’.[/li][li]In the key name field, type in “soft” and click ‘OK’.[/li][li]Go into HKEY_LOCAL_MACHINE -> Soft -> Microsoft -> Windows NT -> CurrentVersion -> Winlogon[/li][li]Edit the value for “Userinit” and change its contents to “[B]C:\WINDOWS\system32\userinit.exe,[/B]” (including the comma)[/li][li]Edit the value for “Shell” and change its contents to “[B]Explorer.exe[/B]”[/li][li]If Userinit or Shell are not present, create them as a new string value and use the above values.[/li][li]In the left column, collapse all the folders until you’re left with just “HKEY_LOCAL_MACHINE” open. Click on ‘soft’, then go into the file menu and select “Unload Hive…” and confirm.[/li][li]Shut down & reboot the PC to see if you can get in Windows now.[/li][/ol]