Can't get rid of "navidad worm"

Hi. Sorry for the long post.I originally started this thread in the hardware forum because evey time I click on a .exe file, I get an error that says windows cannot find the file. If I try to open control panel, I get "windows cannot find "C:\WINDOWS\EXPLORER.EXE". My isp recently threatened to shut me off because they said I have a virus that's sending out malicious emails. I ran a MicrosoftAVbeta scan, which told me I have something called "navidad worm". I looked this up and found this page,http://www.f-secure.com/v-descs/navidad.shtml which describes the virus, along with the exact problems I'm having (unable to open executables, malicious emails). There's also a regedit file to download. It says on the page that All I have to do is run the regedit, then delete the virus files manually or with AV. When I run the regedit, notepad pops up with a few lines of text on it. Then I run the Microsoft AV scan again, which finds "navidad worm", and says it's cleaning it, but I still have the problem. I also downloaded a "navidad removal tool" from the symantec site http://service1.symantec.com/sarc/sarc.nsf/html/W32.Navidad.html but when I run it, a little window pops up saying my system is not infected, but when I run the MS AVscan,it still finds "navidad worm" every time. The only way I can open any of my programs is to right-click a text or picture file or something, and select "open with..Internet explorerer, or Av, etc.., which is how I'm typing this now. Again, I'm sorry for the long post, and I'll greatly appreciate any advice you guys could offer, because this really blows. Thanks in advance!