You know I am going to disagree with the advice about back ups in most cases.
1) For 99% of the population there is no reason do any back ups as most people have nothing on their PC worth backing up so it is in my opinion a better option in a situation like this to just reformat and reinstall Windows from scratch as it tidies things up, you get better performance and you get to reinstall and repatch your software and up to date software and drivers is a good thing.
2) For those that do have things they wish to secure, you should never save it directly to your computers hard drive just put it straight onto an external hard drive or back it up to dvd/cdrom if you get into this habit you will not clutter your hard drive and need to spend days trying to kill any bugs you get.
3) One of the problems with copying things to a back up drive after you are infected is that you may well be copying the virus source as well only to copy it back when you restore.
So my advice just bite the bullet and reinstall Windows it is quicker in the long run.
You are correct Monty
And this is why I keep only the things I can't find anymore and still want on disk, and just redownload everything else.
I had a complete system backup once, I mean everything, all I did was put a new hard drive in and connect this thing to the computer, and it put everything back exactly like it was before, viruses and all LOL
Ever since them I have been doing it the way I do now .