Problem with reinstaling Windows

Hello all!

I have problem with my computer. I am trying to reinstall Windows 7 on my computer.
When i start to reinstall my screen goes black and in the middle there is a message
"No video input" and after that i am getting new message "entering sleep mode". Than i can hear Bip sound and i can hear like computer is restarting but on my screen i still see message in little box " Entering sleep mode". Computer is still working after this all the time. So every time when i am trying to reinstall - it happens after 10 seconds of the time that i am starting with instalation. Can somebody tell me pls. can i do something in BIOS do stop my computer to enter the sleep mode all the time? Thnx in advance.
P.S.Also i forgot to mention that when i am pressing F8 button i cant enter Safe Mode.

It sounds like your video card is not putting out a signal or the video cable is disconnected. What exactly were you doing to the computer that you now have to reinstall windows? Did you disconnect your cables to work on your machine?

Some computers have more than one video output; usually if a video card has been added then the onboard video is disabled so you must be plugged into the correct video slot.