I doubt that you have the lsass.exe virus. How do you know its a registry error? Can you post a screen shot of it? But if you do have the virus do this:
Before you begin:
If you are running Windows 2000 or XP, and have not yet done so, you must patch for the vulnerability described in Microsoft Security Bulletin MS04-011. If you do not, it is likely that your computer will continue to be re-infected.
What to do if the computer shuts down before you can patch or get the tool
This threat can cause Windows to keep shutting down and restarting. This can prevent you from installing the Microsoft patch or downloading the tool described below. To prevent the shut down, do the following. (You may have to try this several times, as you only have about 20 seconds to do steps 3 to 6.) (This will not work on Windows 2000.)
Disconnect the computer from the network/Internet connection. (Disconnect the cable if necessary.)
Restart the computer.
As soon as Windows opens and you see the Windows desktop, click Start > Run.
Type:
cmd
and press Enter.
Type:
shutdown -i
and press Enter.
In the Remote Shutdown Dialog that opens, do the following:
Click Add and type your computer name into the appeared window. Then click OK.
In the "Display warning for <number of seconds> Seconds" field, type 9999 in place of the default value of 20.
Type any message in the Comment box.
Click OK.
Reconnect the network/Internet connection.
Connect to the Internet, and get the patch. Then continue with the steps described below.
This gives you about three hours to get the patch installed, update the definitions, and so on.
When you have patched for and removed the threat, you can re-enable the 20-second default warning if you want to.
Sasser Removal Tool
