The nice folks at ConfickerWorkingGroup.org have whipped up a quick little ‘eye chart’ to tell whether you might have this particular family of malware on your system. It works because one of the symptoms of the software infection is that your PC is reconfigured to block (or redirect) access to certain web sites (like Microsoft, and several anti-virus and anti-adware tools). By trying to see whether certain images hosted on those blocked sites are still visible, you can have a quick indication of whether to be concerned.
Whether or not your PC ‘passes the eye test’, we recommend that you keep firewalls, anti-virus, anti-adware, and operating software fully up-to-date and running at all times — even if it means that your machine runs slower because of it. Your data is just that important.
Conficker Eye Chart
(Go visit the whole Eye Chart page for information on how to interpret this quick analysis: http://www.confickerworkinggroup.org/infection_test/cfeyechart.html)
Another tool that will do a quick detect of symptoms (not a full scan) is here: http://iv.cs.uni-bonn.de/fileadmin/user_upload/werner/cfdetector/.
Symantec provides a free removal tool and comprehensive instructions at Symantec.com/security_response/writeup.jsp?docid=2009-011316-0247-99 .