Hugh,
One of the things you may have found in previous posts is that it's generally advised to run BOTH AdAware and SpyBot S&D. I've been doing that for a year or so now and have definitely seen items missed by each of them. You can generally prove this to yourself by alternating which of them you run first during any housekeeping sessions.
It does, of course, beg the question as to what else is being missed by BOTH of the applications.
If problems, possibly attributable to malware, persist, that's when E-Liam and Richard recommend running HiJack This! which is a bit more into "Techie" territory and is generally advised to be done under the guidance of a suitably tame guru.
Hope that clarifies.
Regards
ST