Virus take over, Windows reinstall

So, my computer has been infected with Malware before and I've managed to remove it with Malwarebytes with relative success. However, I was recently infected and this virus has disabled my access to ANYTHING i can use to remove it. MWBytes tells me I don't have permission to access this or any executable files. I've tried uninstall, but that was just too easy. The program(s) are Malware Doctor 2010 and another I cannot recall.

I no longer have access to Windows at this point. (It will boot the Intel screen, but just goes black at instead of loading Windows.) I would like to try un/re installing Windows, but I don't know if there's any "backdoor" to the operating system.
Thanks!