reseat cpu again, reseat RAM, check mobo's debug LED display if it has one. Check power connections (24-pin and 8-pin) to see if you knocked one loose by accident.

make sure you plugged in the cpu fan since that's what you were messin with

i think it usually beeps at you if you forget that one though

Just tried reseating all of that stuff and nothing changed. Power connections are plugged in. CPU fans as well (I can see them spinning).

All of the fans that I can see are turning on but it won't power on

Did you check the motherboards debug display? google the number

There isn't one on this mobo -- it's a g1.assassin 2

Any beep codes at all?

Which CPU? Have you tried using the onboard GPU if there is one?

Try a hard reset, unplug main power cord from the tower, hold power button down on tower for 15 seconds, plug power cord back in and try turning computer back on again.

And this is a no POST issue Slin.

I had the same problem awhile back, and it turned out that I never installed the standoffs on the back of my motherboard to keep it off the chasis of the case and it was grounding out..again..and again, until I realized. Did you ever install them? Maybe you've just been lucky until now.

Look like this:

http://www.cybergooch.com/tutorials/images/buildsystem/IMG_6805.jpg

Edit: bad image link?

make sure you didnt bend any cpu pins putting the cpu back in, and make sure you put it in properly. also try what testify posted.

Sounds like a mobo problem. Do you think you might've killed it with ESD?

uh ok so I got frustrated and took a break. got some coffee, came back, and i turned it on and it works now. magic i guess?? still have a problem though.

computer boots up, fans running, everything looks and sounds great. only one problem:

no signal to monitors. no post screen telling me to hit f8 to go to BIOS. when i first built this rig i was able to solve the problem by taking out my GTX 770 and putting in my old GTX 580. Apparently the mobo has an issue with the 770 and I had to set the pci slot to legacy pci something something so that it would get along with my 770.

anyways even with the gtx 580 in it doesn't show anything on my monitor. uh oh.

---

edit

i really should write down instructions to fix this problem cause i had it before. anyways i put the gtx 580 in a different pci port and also realized that my keyboard and mouse were unresponsive. i try plugging them into different USB ports and get mixed results. some usb ports the two keyboard lights will turn on (caps and num lock) and stay on -- pretty weird. i tap a bunch of buttons and nothing happens. other ports there's no lights on. tap buttons, same result.

Sounds like your mobo might be damaged

But did you check the standoffs.

yes i did sorry they're in.

this shouldn't be a crazy issue like all i did was take out the cpu and put it back in. and then reseat the RAM and stuff. the computer was working fine like 5 hrs ago.

but yea this is a bleh situation. also thanks for trying to help me out guys.

no bent cpu pins.

CPU: i7 3930k
GPU: GTX 580/770
16 gb ram which i'm trying to move around for different results lol
and the mobo is a g1 assassin 2

Your mobo seems to have really bad reviews. Have you tried flashing a new BIOS?

it's magic i swear it just started up ahhhh yes so happy

if anyone uses google and finds this thread just know that plugging in random stuff and moving things around randomly to hope it works might work.

and thanks platypus

You reseated the RAM? Same slots?

Is the RAM one 4*4GB kit? Put it in the proper slots (read the manual) or just use 1 DIMM and test with that.

Edit:
Reading the manual and putting the GPU and RAM in the slots they're supposed to be in instead of where they best fit (yes i know huge heatsinks are a problem) could've saved you a lot of time.

K semi false alarm.

So I was able to get the entire setup working with my GTX 580 and 1 stick of ram in slot #1. I then changed the setting to legacy and put in my 770. It works still. When I try to put in all 4 sticks of ram I don't get the post screen...

and yea its 4x4. the 4 sticks are different? i thought they're identical. i just know you put the in in a specific order 1234?

but you're right it's something to do with the ram cause if i only run the 1 stick in slot 1 it works fine. I then shut my computer off and put the second stick in slot #2. start it up again and it fails to boot.

So check each stick of RAM and each slot individually?

smart.

ok so i tested all 4 sticks in only slot 1 and they all work.

then i tested just 2 sticks and found that the only configuration that works is slots #1 and #4.

then i tested 3 sticks and found that any 3 stick combination doesn't work. both keyboard lights are on.

and any 4 stick combination doesn't work either. no keyboard lights are on.

read the mobo manual -- all it says is stick the sticks in the slots. found nothing on the gigabyte website either.

Your mobo is bad.

Slots #1 and #4 as in DDR_1 and DDR_4 (they are labeled) or as in first and forth slot aka DDR_3 and DDR_4?
Are all of the sticks identical? There should be a huge number/letter combination on a sticker on them. Have you tried placing two sticks in DDR_1 and DDR_2 (the green ones).

The manual says

http://download.gigabyte.eu/FileList/Manual/mb_manual_g1.assassin2_e.pdf#page=16

they're labeled.

Slin I had the same exact problem but a different mobo. If you tested each ram stick and they work; but with all four in it doesn't; means you have bad ram slot(s). You either have to not use the bad slots, or get a new mobo.

*edit* Check to see if somehow the slot(s) got lose. It may just be an easy solder fix. Your mobo got shorted out or its bad build quality.

That means the #2 + #3 link on your mobo ram slots have gone bad.

Slots #1 and #4 have a link but are still good while #2 + #3 the link has either malfunctioned or shorted out.

I'd contact your motherboard manufacturer if it's still under warranty.

Have tried booting with one stick in slot2 (same with slot3)?

If you are too lazy to look at the sticks then I can't help you, just run dual channel or buy a new mobo.

Had this issue. All i did was switched the voltage back and forth a couple of times and it worked idk how.

FYI changing your voltage like that is a good way to ruin your board. If it's working leave it as is and consider yourself lucky.

Slin, your board is damaged or something isn't grounded properly as mentioned above. I would assume more that it is damaged (ram slot issue you are having obviously) as it seems to be hit and miss with how you are getting it to power on sometimes. It almost sounds like a charge went through your board at some point...i'd salvage the remaining parts and just put them in a new board.