Question Old PC wont detect Monitor, mouse or Keyboard

[Patolek]

I dusted off my old (8 years) PC which I haven't used for about 2 years and now when it turns off It just doesn't give any signal to my Monitor, Mouse or Keyboard. The screen has no signal therefore I can't acces BIOS or anything like that.

I've tried switching my GPU to a different socket but that didn't seem to do anything.
I've also tried resetting the cmos battery by removing it for 5 minutes, also didn't fix it.
I've tried plugging it into a different monitor, through HDMI, DP and neither worked, I'm 100% sure it's not the monitor or the cables because I use all of them on my main computer and they work fine.

So what could be wrong with my PC? It couldn't have just broken even tho I didn't use it?

I heard that sometimes replacing the CMOS battery helps, as those tend to fail after a long time but my fans and everything are spinning and lights on my GPU are shining so idk if CMOS has anything to do with this.

I also read to update the Motherboard bios because it might be out of date, however I can't see my monitor so It's kinda hard for me to update it. Unless I try putting it on a disk but not sure hot that'll work.

Any help would be much appreciated.

 

[Vic 40]

Swapping the motherboard battery might be a good place to start, leave the socket empty for a good 15minutes and then put the new one in.

Does the cpu have integrated graphics? If so take the dedicated gpu out and start by using the igp and connect the monitor to the back I/O from the motherboard.