Pc boot issiues

Try rearranging the boot order of your HDDs in the system BIOS - with one disk temporary off line the other will have been promoted to "first boot disk" but won't have the info on it.

Already tried switching it all up it didn't work by now

"The monitor just is black can't even let it boot into BIOS", "Already tried switching it all up", what are you switching if you can't see the settings?
Make sure you haven't unplugged/loosened anything else in the case

I'm switching the cables! It doesn't even boot up Into BIOS! Already tried just having one plugged in.

Still doesn't work or boot up.

You need the cables in the same place they were at the start.  Always unplug/replug with the power to the PC off.

The computer isn't really interested in which port the HDDs are attached, it's looking for the same combination of drives that were there originally.  Then it needs you to tell it (in the BIOS Boot Order) which one to check for boot details first.

The blank screen is unrelated to that, even without any HDD you should still be seeing something on the screen. That's why I think either something else is loose or damaged.

Do you know the make & model of the PC?

Assuming you know which one of your HDs is the boot disk (so you remember later), if you haven't already done so, I'd disconnect BOTH SATA HDs, and go from there to try to at least get into the BIOS?

It's a second hand self build Pc.

Asus motherboard
2x Seagate HDD 320 Gb (one of the. I unplugged)

Now trying every combination possible (with the Pc turned off) it still doesn't work even if BOTH HDD's are unplugged. Hope the pic helps (there i have the two sata cable laid on the side with the power cables there too. Still a black screen)
20180429_105922.jpg

If you're not getting any startup beeps, and both HDs are disconnected, remove the memory sticks and see if the PC complains.
If it does, put them back in.
Does the mboard have on-board video, if it does, remove the video card, and plug the monitor directly into the mboard and see what happens?

My Pc (at least i think) doesn't have a beeper. Hold on
20180429_111248.jpg

Why was the drive removed originally?  Any problems preceeding these?

Getting the screen responding would be my first priority - the data on your drives is almost certainly safe.

See if you can force some beeps through missing memory sticks as IT-Expert suggests.

Nope... Still doesn't work after taking out all ram thingies. And no I can't disconnect the GeForce since it has the only port for the monitor.

I left the side of my Pc open due to overheating issues and saw it unplugged this morning. Plugged it in again and... yeah. Now I'm here :/

We're getting close to being stuck here I think!
I'd expect to get some sort of audible warning for the missing memory.
I'm wondering whether a BIOS reset might be a good idea?
Need to focus on getting either beeps or screen.
Are there any diagnostic LEDs on the board, that might assist you, that you know of?

Shouldn't be overheating, so sounds like another issue there?!

Uhhhmmm.... how do reset my bios..? Also no. I DID hear the HDD'S spooling up and beeping but with them disconnected the Pc itself doesn't make ANY sound except the fans...

Nah it never turned of due to overheating or anything but the Gtx240 I have is so f***** annoyingly loud I opened the case for extra cooling. Let me guess that was idiotic from me to do? :D

Hold on imma get another monitor and cable... i swear to god if thats the problem...

Nope. Still dead

I hope you meant taking out this
20180429_114148.jpg

THE RESET WORKED IT BEEPS NOW :DDD
20180429_114920.jpg

Now it asked me this :o

I have to say the bottom of it has a layer of dust that needs so e cleaning :/

Oops forgot the image!
20180429_115120.jpg

I dont know if the reset worked it the battery i did both at the same time

You should just be getting that msg, because there aren't any bootable drives attached.

Great, now try to put both drives back in to their SATA ports
There's a 50:50 chance it will reboot into Windows otherwise it's boot into BIOS and swap over the boot order for the hard drives.

Progress!  You can start calming down now, your PC is going to be back soon :)

But the drives are connected!

Oh okay doing the swapping. Here's me hoping i know wtf I'm doing

It's alive! And I'm in. Thanks guys!
20180429_120034.jpg

Thanks again!