Avira Rescue System is a free bootable antivirus program that you can run from a disk before the operating system boots. It has a familiar, point-and-click interface that makes it easy and intuitive to use.
Avira Rescue System Review
Avira's Bootable AV Tool isn't my first choice because it doesn't always work. But when it does, it's a great tool.
This program is downloaded as an ISO file. Once it is on your computer, it needs to be burned to a disc, then your computer needs to be restarted so that you can boot to Avira Rescue System before the operating system starts.
The first screen when booting to disk asks if you want to start the program or boot normally to your hard drive. Obviously you want to choose the first option, so press Enter on the Start Avira Rescue System option.