I've been looking into the DNS-changer worm that's scheduled to hit on Monday for Gellin. The bottom line is probably most people dont need to worry.
Go to http://www.dns-ok.us . This site was created to identify computers with the problem. As long as you get a good green splash page you don't have the problem.
If you get a red page with a warning then they will tell you what to do; you can also go to http://www.dcwg.org/fix or to http://www.opendns.com/dns-changer . The fix is simply to change your dns settings to something reliable by going to control panel->Network Connections->(your connection)->Properties->TCP/IP V4 Properties and set your DNS to something valid.
If you get caught by this and don't know what to use, Google provides a free and open DNS server at 22.214.171.124 which should be easy to remember.
What happened is that years ago, this software was installed on a number of PCs by bad web sites. It forced them to use bad DNS servers to resolve addresses (so the bad guys could send them wherever they wanted).
The FBI caught on, shut them down, and replaced the bad DNS servers with good ones. The substitute servers are old and will be turned off Sunday/Monday at midnight.
If you were pointing at them, you suddenly won't be able to access any web sites because there will be nothing to translate names like google.com to IP addresses.