You might try this:

http://www.ewido.net/en/

It has over 87,000 items in its database

It is payware, but you can download a trial. After that has expired you can Still update it and use it as a manual scanner, for free.

I also like SwatIT, it takes forever but is very thorough.

http://swatit.org/

I think that these two are somewhat better with trojans and worms that the others.

I agree with HTRegz, in that you should run your updated AV in safe mode and do an online scan.

You should monitor the registry and check for new programs:

RegistryProt from DiamondCS http://www.diamondcs.com.au/

This is also a useful tool that warns you of new executables on the block:

http://www.winpatrol.com/


Other than that, I think you should warn people more about using HijackThis! It is not a tool for the uninitiated. They should be sure to back up the Registry before manually deleting things.

Cheers