Pc will not boot up on power up

Hi guys, I have a modified HD Pavilion 500-199. Only my moBo and processor are original to the machine. I run an ASUS strip get 960, a 500w dynex power supply. I have 3 drives in my rig. One 120gb Kingston ssd. And two 1TB hdds. 16gb of crucial ballistic ram. This is all wrapped up in a Zalman z5 series case.

I was running into an issue with windows 10 and missing network protocols. And after troubleshooting that problem several times with no luck I decided to wipe my current windows install and start over because everything was working fine up until I ran some updates a few days ago. So I made a windows 10 installation usb and went to boot up to run off the stick. My PC kept beating me to the windows load screen so I hit reset this happened 3 times. Then it would power on and I got nothing come up 8 my screen and my mouse and keyboard wouldn't power up. So I pulled the main power cord and let it sit for a few. Plugged it back it fired her up and still nothing. I can here the fans power and the hard drives tick. But that's it. So as I sat here looking up on my tablet having a WTF moment, bam! Windows load screen flashed up. I didn't logon to windows I just clickthe power icon and said shutdown. After she powered down I wanted to try and boot off my usb again. So I hit my power button the fans fired up I could here the hard drives but nothing on screen. So I called my PC a few choice words and pulled the power cord again. I disconnect all my peripherals with just my monitor plugged in and nothing. Same thing again. So I opened her up and cleaned all the dust out there wasn't that much in there I was pretty surprised. I reseted my graphics card, my ram, the power cables put it all back together. Plugged her in fired her up nothing. So I did it again this time I even popped out the cmos battery put it back. Hit the power nothing same thing again... now I'm frustrated and don't know what else to try. So I found you guys looking for help.

Little update: I tried disconnecting the drives and powering on I get nothing, even just trying one at a time. Sometimes it powers down then fires back up on it's own but not actually booting. Did my power supply bite the dust?

Update 2: I just bought a new psu and the problem still happens I am officially stumped

  Fruit Bat /\0/\ 22:38 27 Feb 16

Switch off at socket

press and hold power button for 30 secs

reconnect and retry to boot

Hopefully will get rid of any residual static on MB.

  bumpkin 22:59 27 Feb 16

* Sometimes it powers down then fires back up on it's own *

Long shot but check for a damaged usb port.

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