X: prompt is all I can get to

None of the troubleshooting methods worked when the blue screen appears after over an hour of efforts to correct my hang-up on my primary PC. I finally settled on going to DOS and got an X: prompt. All I could I remember about DOS is how to change drives and list directories and files. My ACRONIS installation disk says it is bootable. How do I get to and execute a reboot and then fix the problem Comcast and my irritation caused? After the Comcast repairman switched out a Video box and left, my screen kept opening a window asking me to initialize my products. That just tied up the replaced box which was already working fine. Except for Xinfinity chat, there was no way I could get to any of my favorite web place. I got sick of non-solutions and tried to restore my PC to last Sunday which failed leading to your troubleshooting screen where only a X: prompt is available. On your disc I see setup.exe but that is probably for installing the product not clean booting.

How to I get back to operational? If I can get back to Windows I can try to get help from Comcast