AVG offers a solution called AVG Rescue CD. This can be deployed to a CD or a USB device.
To copy it on the USB device, firstly download the archive from the download page: http://www.avg.com/us-en/download.prd-arl
Extract the archive to the USB drive then run makeboot.bat. Make sure to select the drive letter assigned to the USB. Once the process is finished, restart the PC and boot from the USB device.
For more information access the following page: http://free.avg.com/us-en/226162