I disreccomend AVG due to the fact that it's services make my dad's laptop run slow. Runs fine without it. If you can bear this, use it, it's great (I used it for 3 years.) I now use Avast.

My opinion on how to remove rootkit:
1) Get Linux Live CD or USB (Ubuntu)
2) Start Linux
3) Open Terminal
4) $ ls /dev/sd* #One of them will be your hard drive
5) $ sudo mkdir /mnt/hd #For mounting hard drive
6) $ sudo mount /dev/sd?? /mnt/hd #To mount your hard drive
7a) Find the root-kit and delete it
--OR--
7b) dd if=/dev/random of=/mnt/hd/[Wherever your rootkit may be] #Linux is case sensitive, and spaces are done like this: Documents\ and\ Settings. This command writes random data over the rootkit, thus killing it. Delete it once you reboot.
8) Restart into Windows.

I hope this works. I didn't test it. Using dd is dangerous, make sure you know what you are doing.

Cooper