AVG is a fine anti-virus program that I used now and Microsoft is now offering a free anti-virus program that you might wish to look into.
Myself I layer my protections.
I strongly suggest adding the free version of a program by the name of "sandboxie" and running all programs that interact with the internet inside it. Any malware that get by your other protections will be removed from your system as soon as you clear the sandbox at the end of a browsing session. Also if you are not sure of any other program you might wish to try on your system you can at first install it and run it inside the sandbox.
I also am very very happy with a non-free program by the name of "Process Guard " that will not allow any program to run on your system until you clear it to do so and any program that had change because of an update for example or because of malware for that matter. It also block keyloggers hooks and offer protection to memory along with others protections not build into the OS until Window 7.
Sandboxie had the ability to do this, however if you do not run sandboxie I would also strongly suggest, if you are running XP or earlier OS, to used a Microsoft program by the name of "DROPMYRIGHTS" with any software that interact with the internet. This limit the ability of any program that had been successfully attack by malware to do changes on your system such as to the register.
Last note I would suggest you start to listen to a one hour weekly podcast by the name of Security Now to keep you inform on security threats.