You need to have a clued in user, but I have used:

winpooch:

http://winpooch.free.fr/

It adds on access scanning to clamav (and has a built in clamav scanner to
do away with clamav installation plus the ability to use other av scanners).

The software is not for folks that don't know what is running on the machine (most
users), but can be good for folks who want to know what is going on.  It can
be tuned via rules to allow the usual background processes to not annoy the
heck out of you (otherwise they pop up on schedule to have you allow or deny the
process).

Kelly Black
KB0GBJ