Free:
http://us.mcafee.com/root/mfs/default.asp?cid=9914
Trend micro also does a free 'house call' applet that runs from their website.
You can also download the free 'stinger' tool here to remove various threats:
http://us.mcafee.com/virusInfo/default.asp?id=vrt
Run it on all suspected pc's.