U have to be careful where you get it from. It's strongly recommended to only download it from combofix.org.
Anti-spyware can mess it up, so it's recommended to close those before running. AVG hasn't messed it up when I ran it.
EDIT: I did have it remove a file that windows needed to boot. If I remember correctly, it was infected anyways. It lists the files that it's gonna remove and keeps a good log of what it does. The file it removed was easy to replace.
Oh, and I give CNET about as much weight in my opinions as I do CNN. :jester:
Copy your hard drive or whatever and get the new 1 setup, then you could try combofix just for S&G. I'd personally recommend combofix before getting a HD. I also do not believe in reinstalling windows to fix problems like this as the same problem will crop up again unless you find out why it came about in the first place or how to stop it from happening again.