PC not going through POST

I built a gaming PC a couple of months ago and yesterday when I tried turning it on it wasn't going through POST. I tried running it bare bones with just the mobo, cpu, 1 stick of ram and graphics but nothing. I also tried ruling out the PSU by using a PSU from another system that I know works and that didn't work. The really weird thing is now my other system isn't going through POST either. Is there something that can be transferred from my mobo to my second PSU that's making it not work?

Transfered, No, BUT, if the board in the initial troubled system has gone, it may be possible it has failed, possibly shorted, and using another PSU it may of been possible it has damaged that through some freak feedback or something, do NOT connect ANY other PSU to the initial troubled system, if this is whats happening it will get very expensive very quickly. Trying a bare bones boot is a good move, but the fact nothing has happened makes me fear the motherboard has gone bad, unfortunately there is no clear cut test to prove this, all you can do is prove all the other components are good so only the board is left, then it becomes a leap of faith. When you say no post, does ANYTHING appear on the display ? like in dos mode ? If it does are you able to enter the bios and check system health for a temperature reading ? Do you by any chance have or get a PSU tester ? it would be good to see if these report the PSU's as bad or not, especially the one that was proved working. What power socket are you using for this\these system(s) ? what I am wondering is if the working PSU came from another power socket, basically I'm wondering if it may be a bad socket in the wall. Best advice I can offer while awaiting answers to these questions, is first visually inspect the motherboard (the initial problem one), look for any sign of blown components on the board, if they are totally blown they will be obvious, more so if they are leaking, otherwise it may be a more subtle kind of bump where it's starting to push out from within, also try and smell the board, see if you can detect any odour, if you have ever smelt bad electrics you will never forget the smell, it's that distinctive, this is what your trying to see if it has such a smell. Lastly the only other thing to try is strip the system to bare bones again (using safe precautions as you presumably did when building it), then remove the motherboard, place it on a non conductive surface (try smelling the PSU's for the same), say cardboard, or even the boards own box as it will aid seating the video card) leaving the rear edge over the edge of something so you can put the video back in, then see what happens with it out of the case, it will help you see if there is any possible shorts, and you can inspect the back of the board for signs of damage as well. This gets you started at least, but I fear it wont be an easy one, and it might be expensive, because so far we have 1 possible bad board, and 2 PSU's that may be bad, but I finish with another question, do you have any sort of surge protection ?

Transfered, No, BUT, if the board in the initial troubled system has gone, it may be possible it has failed, possibly shorted, and using another PSU it may of been possible it has damaged that through some freak feedback or something, do NOT connect ANY other PSU to the initial troubled system, if this is whats happening it will get very expensive very quickly.
Trying a bare bones boot is a good move, but the fact nothing has happened makes me fear the motherboard has gone bad, unfortunately there is no clear cut test to prove this, all you can do is prove all the other components are good so only the board is left, then it becomes a leap of faith.

When you say no post, does ANYTHING appear on the display ? like in dos mode ?
If it does are you able to enter the bios and check system health for a temperature reading ?
Do you by any chance have or get a PSU tester ? it would be good to see if these report the PSU's as bad or not, especially the one that was proved working.
What power socket are you using for this\these system(s) ? what I am wondering is if the working PSU came from another power socket, basically I'm wondering if it may be a bad socket in the wall.

1. The monitor gets no signal from the PC at all. I know the monitor works because I tried it.
3. I have a PSU tester and it says that both of my PSU works fine but the fans from the second one on the other system no longer works now =/

So is this purely a no display issue ? or does it not spin up at all ? The PSU's testing good means everything should be spinning up and whirring away like a trouper, if this is happening then the video is the next place to look\test. As to the fan not spinning in the other PSU, have you rechecked the tester and made sure the voltages are right for each lead ? it could be simple coincidence that the fan has just chosen to die, if this has happened then it may be possible to change the fan, BUT, I strongly suggest taking it to a repair place for that, there are currents powerful enough to kill you if you touch the wrong part inside the unit, so is best done by those trained to do it, see if this helps.

Well all of my fans including my CPU and GPU fans spin when I power it on but it just stays like that. My monitor gets no signal and it isn't the monitor because it's the same issue with every monitor I try. Also when I take out all of my RAM I get no beeps at all like I should.

ATM the graphics card is the weak link, do you have another card you can swap in for testing purposes ? and try this card in another system ? Proving the graphics card to be good or bad is really needed to be able to move on, it may well not be the card, but until we can prove it one way or the other we wont know where else to look.

I don't have another graphics card for testing but could it really just be it? I mean I've tried booting with just the Mobo and CPU with no graphics or RAM and even then I don't get POST beeps.

There is no sure way to say without being able to test it, can you ask around a few mates to see if they have a system\card who could aid with testing this ? No beeping does raise questions, but not all boards\systems have speakers so beeps can't be heard, but it could be the card slot on the board thats gone faulty, but as a board can never be 100% diagnosable, we really need to prove the card one way or the other so we can move forward, so if you can ask around and see if someone has a spare card to test with, or would be willing to test your card in they're system at least you can move on.