you could try MS own sasser removal tool if it is sasser -
http://www.microsoft.com/security/ma...e/default.mspx
also from MS -
Win32/Sasser.A is a network worm that exploits the Local Security Authority Subsystem Service (LSASS) vulnerability fixed in Microsoft Security Update MS04-011. The worm targets Windows 2000 and Windows XP computers that have not installed the MS04-011 security update. Infected computers attempt to spread the worm to other unprotected computers by randomly scanning IP addresses and infecting vulnerable computers.
also ..
ms information on one of the variants of sasser