I installed a new power supply and my PC still won't turn on.

[Clumpy]

So my computer wouldn't turn on, I pressed the button and nothing happened so I looked around on forums and found that it was probably my power supply, I ordered a new one, changed it and it still doesn't work. I'm really stuck now. I've tried several power cords and plug sockets and nothing is working.

 

[Supermonkeyf]

Did you build this computer yourself?
Is the power switch connected to the motherboard properly?
Is the power supply itself turned on?

 

[Clumpy]

Did you build this computer yourself?
Is the power switch connected to the motherboard properly?
Is the power supply itself turned on?

I built it with my friend. I'm pretty sure all the cables are in the correct place and the power supply is turned on. I think the power switch is plugged in correctly.

 

[USAFRet]

Is this a new condition?
Did it ever work?

See this series of diagnostic steps:
http://www.tomshardware.com/forum/261145-31-perform-steps-posting-post-boot-video-problems

 

[Clumpy]

Is this a new condition?
Did it ever work?

See this series of diagnostic steps:
http://www.tomshardware.com/forum/261145-31-perform-steps-posting-post-boot-video-problems

Yes, it was working for about a year before this happened and it has been broken for around 2 months.

 

[USAFRet]

Is this a new condition?
Did it ever work?

See this series of diagnostic steps:
http://www.tomshardware.com/forum/261145-31-perform-steps-posting-post-boot-video-problems

Yes, it was working for about a year before this happened and it has been broken for around 2 months.

What was the last thing you did before it wasn't working?

 

[Clumpy]

What was the last thing you did before it wasn't working?

I just stopped using it for about 3 weeks and when I came back it wasn't working.

 

[USAFRet]

I'd suspect some cable is loose. Go through the link above, and check everything.
Don't just read it....verify everything.