If your screen is blank you have a display problem or your comp doesn't even POST. if that is the case then the bios would be the problem. Most of the time with a virus erasing the os you will get a post screen, sometimes just a logo and then I may say insert a boot disk or invalid system disk. This means either you master boot record is bad or you are missing major system files like the kernel.
Do you get a POST or banner screen?
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