AVG Rescue CD (for USB stick) is a free download for anybody, cleans viruses from Windows or even Linux PCs, and is a great addition to your PC repair toolkit.

The AVG Rescue CD comes in two flavors: an ISO image that can be easily burned to an optical disc, or a compressed version that can be installed to a bootable flash drive. Once you've done so, you can simply boot from the drive of choice directly to the AVG menu, where you can scan for viruses, edit files, test your drive, or even edit the registry. Since the bootable CD is based on a version of Linux, you can also access a number of common Linux tools to make changes to your system and hopefully make it bootable again.

How to create AVG Rescue CD (for USB stick)
Following steps tell you how to install AVG Rescue CD files onto a USB pen drive. The steps for installing it on a CD would be a bit more complex because you would need to download the iso file and then burn it onto the cd and make it bootable. Doing it on a USB drive is easier though.
1. Download AVG Rescue CD (for USB stick).
2. Plug USB flash drive in the USB port of your PC.
3. Now extract the downloaded AVG rescue RAR file in the USB drive.
4. Open the drive by double clicking on it to see all the files inside it.
5. Locate the "Makeboot.bat" file and double click on it to launch it.
Warning: Never launch this "Makeboot.bat" file from any other drive other than USB drive. If you launch it from the system drive, it will make it unbootable.
6. A command line window will appear.
7. Press any key of your keyboard. Wait for few seconds. After some time a message will pop up saying "The AVG rescue USB should be bootable now".

The license of this software is Freeware, you can free download and free use this boot cd software.