You might try using
BHOdemon.
The exact same hijacker was installed on a friend's system and running Ad-aware, Spybot, and SpywareBlaster did nothing. There is a hidden DLL file in the \Windows\System directory that wasn't identified by any of the those programs and can't be deleted from Windows.
I used BHOdemon to identify the DLL file (in my case it was mndmsm.dll or something similar). You'll need to boot to a command prompt (use a Win98 or WinME boot CD) and delete the DLL file that BHOdemon shows. Reboot into Windows and use the registry cleaner in BHOdemon to remove the registry entry.
Worked great for me for this exact hijacker.