Rather than going to the expense of purchasing a different antivirus product, and since you have AVG already, why not go to the AVG forum for assistance.
Purchase it here or you could search for a boxed version at a local retailer (you may find some deals now as 2010 versions are fixing to come out soon; they are in BETA now. And do not worry, your subscription to 2009 product will transfer for free to the 2010 product when it is released.)
You will need to run the AVG removal tool several times to remove all of it. You may also not get a good installation of the Norton product, I would recommend Norton Internet Security, until the rootkit gets removed.
Let us know if you need further assistance with the change-over.
If you have over 600 infected files and dlls then the system is beyond repair. I really don't like telling people this fact but that is just too much of the OS / file system / programs installation to properly repair with out reformatting and reinstalling the OS.
After you do that, I would like to suggest you get a good security suite (one with an antivirus and a firewall) similar to that offered in Norton Internet Security 2009 or 2010.