LSASS.EXE SYSTEM FILE or INFECTION

I have XP and eliminated lsass.exe thinking it was some type of spyware/malware/trojan. However i can't get past the WINDOWS opening window. Is there some way i can reload this file back on to the computer without bringing it to a tech? or do I have to get a CD to reload the file back to the HD? I deleted the file after I tried the "last good configuration" and the screen popped up that lets you know the virus is shutting down the computer. I can't get to the desktop so that is my dilemma.

Do you have a XP Install CD? If so, boot to the Recovery Console (enter R at first opportunity). When you get to the command prompt, enter:

copy C:\WINDOWS\system32\dllcache\lasss.exe C:\WINDOWS\system32

That should put it back.