Hello, I am having trouble reinstalling Windows 7 on a machine. My CD drive connects via USB. I was able to put my Windows 7 Disk in the drive and reinstall the OS no problem. I was even in the desktop install drivers. Then, when I restarted, I got an error message saying "Invalid System Disk." I tried to boot from my USB CD drive, but even when it is the first boot option in the bios, I get "Invalid system disk". How do I fix this? What caused this?