It seems unlikely that a simple antivirus software is going to fix all your problems. Your malware may even prevent you from being able to download them, or it may alter the program upon downloading so that the malware is packaged in (I got hit with that once - nasty). My best advice is to look up antivirus forums (I've used daniweb in the past but they by no means hold a monopoly), the kind that have this sort of thing down to a science. They give you a long series of tasks to do and programs to download and run, the results/logs of some of which you post up in your help thread.
To recover your files, if they are still on the computer, a very good trick to use is to burn or find a Ubuntu LiveCD.
https://www.ubuntu.com
Ubuntu is a Linux distro. The point being you can boot up a separate, non-installed operating system from the CD, taking you out of the malware infested Windows setup and letting you view all the files on your hard drive, as well as save them. The malware may not have removed the files, and may only be interfering with your ability to access them via Windows.