Hi, I recently bought a used computer which worked completely fine until I installed an old HD (60gb) I had an older computer which failed after 2 years of use. This is how the failure is described -Powering On , no error sounds, no video signal. Then I decided to install the old hard drive into the new machine. I did so and it seemed not to be detected (so I assumed it was totaled) I plugged the hard disk (which was in the computer before) back in. After that the new computer has the exactly same symptoms as the old one.... Now I´ve got two computers which power on, but do not seem to produce any video signals.. Believe me I´ve tried to pull the battery out(cmos) , Ive tried switching video cards, I´ve tried disconnecting the dvd drives, the sound card.. I´ve also tried new power supplys on them both. Nothing seems to work.. So my question is, is it even remotely possible that by installing the faulty hd from the old computer in the new, that the new computer may have been damaged by it? the old hard disk did get pretty warm, and did make funny noises though. Any ides as to how to fix this or test further?

If it's an IDE drive, make sure you have the ribbon connected right. The red dot should be to the right of the ribbon near the power connector when it's plugged in.

Disconnect any drives. You don't need a hard drive to get a display on the monitor. All that is needed to get a display is a working power supply and motherboard/CPU/RAM.

Thanks for the comments. I tried unplugging the hard disk from the computer, that still left the monitor blank. I also checked if it was connected correctly, and it was. That still leaves me without a VGA signal from the pc :/