I think that there's something not plugged in correctly.
If all that was changed was a PSU, I doubt the CPU has just failed. I would double check all of the connections again.
Also, if you can get the exact POST beep code it would be helpful. 5 beeps indicates a process failure according to this but I'd like to be sure.I've had a friend come over who buys old computers and fixes them up to come over and help me. He didn't see anything wrong with the wiring but he did say it was unlikely that a CPU got fried when a PSU went out. I called the guy who fixed the beeps from the bios the first time and he said that it was 5 short beeps and then repeating beeps.
I think my first post was a LITTLE to vague so I'll try to make what I've done this far a little more clear.
First my power supply stopped working and a friend of mine did the paperclip in the green/adjacent black wires to test it and it was CONFIRMED dead. After that it was replaced by a confirmed working PSU. When I tried to start it up I got 5 short beeps and then repeating beeps. At this point the monitor was still getting nothing. Soon after that I took it to a co-worker and after he moved the supplementary power cord for my graphics card from an extension of a fan to a normal 4 pin connector there were no more beeps. I took it home and when I tried to hook it up to a monitor, the monitor screen just stayed blank. I tried it on two different monitors (both of which are working properly) using an 8800gt, the onboard monitor output, and an old geforce 4000mx I had lying around and still nothing was going to the monitors. After this I had the motherboard replaced, going from an EGS to an ASUS motherboard, both using the same chipsets and everything else. Even after the motherboard was replaced with the ASUS one the problem persisted. I tried using the 8800gt, the onboard, and the geforce 4000mx again and still nothing worked. After this I decided I should try new RAM in case it was damaged when the power supply died. I used two new sticks (both confirmed to be working) placing one in each slot, then switching them, then trying one at a time in each slot. This still yielded no RESULTS and that pretty much leads up to where I am now.
Sorry for the novel but I think it may clear things up a little.
Thanks for all the help as well, I really appreciate it.That's a very clear post, thanks.
You do seem to have eliminated most things. However, try a bench test too.
Take the motherboard out of the case and place it on an anti static bag or piece of cardboard. try to power up using only the bare minimum COMPONENTS, preferably confirmed working. That means CPU, heatsink/fan, one stick of RAM, PSU, and video card.Get a cpu to test it, I dont think that the psu had killed it but rather esd or a bent pin or something the thing is you had tried both boards assumeing that your using the same cpu in the other one that its probably why its not working. Thanks alot for the help. I'm going to get a cheap CPU to test and hope that's the problem.
I tested everything you suggested now Calum and nothing seems to be the cause of the problem yet. I'll update this post once I test the new CPU.
I really appreciate all the help everybody has given me, thanks again.Good hope it works out then.