Sometimes when your Windows gets infected by virus, system files gets currupted and in that case your PC does not start or gives some kind of error. At that time you can use Rescue Bootable CD's to scan your drives, create delete partitions and can perform many other operations.
Last time I told you about Kaspersky Anti Virus Bootable Rescue CD<. If you use Avira Anti Virus, here is Avira Anti Virus BootableRescue CD. Just download it and burn it in CD and you can use this CD in future.
Download Instructions : Click here to download.