Kaspersky has released a free utility WindowsUnblocker that can be used to boot an otherwise unbootable computer and start the process of cleansing the registry of unwanted entries that have been added by malware. The software is supplied as an ISO image that can be burned to CD or DVD, or used to create a bootable USB drive you then simply need to ensure that your computer is configure to boot from that drive and youre ready to start cleaning up your system.
Download the disk image (kav_rescue_10.iso), then use this utility (rescue2usb.exe) to record the disk image to a CD/DVD or Flash removable device.
Read the guide to use this utility on Kaspersky website.