first when did this start happening and what os are you running
if this is quiet recent then start your computer in safe mode.
if you are running windows xp it gives you an option of restoring back your pc to a previous date.
try that,if the spyware enetred recently your computer may have an older healthy copy of registry.
if that doesn't work start your computer in safe mode with network support
and download lavasoft's adware remover se here from antionline's downloads
and try removing the spyware.also close any programs running in the system tray to free some memory space.
also delete your temporary internet files folder and cookies.