So i recently dug my dad's old computer out of the garage and fired it up. Since i didn't have a monitor yet, i borrowed the one off my dad's current computer the first few times. Everything was working just fine and no problems. Then 2 days later, i got an older monitor from my brother for free. I tried using it, but it kept going into sleep mode. I did a little tinkering around and figured out that the computer doesn't even need to boot up for this to happen. The second i plug the monitor into the computer, it goes into sleep mode. Then i figured out that the old monitor works just fine on my dad's current computer, and that all of a sudden, even my dad's monitor doesn't work on the older computer. Any suggestions?