[SOLVED] No boot and no bios and 1 beep

[Helpwithwindowsplease]

So I cleaned my PC today, mainly cleaning fans with small brush and vacuum near to pull dust away. Before closing case I made sure all the fans on case, GPU, CPU and PSU were running. In this weather I was concerned about overheating

Anyway, went to reboot and only get Asus splash screen and a beep then it freezes there. Del and F2 wont get me to bios nor can I get keyboard capslock etc. Tried interrupt 3 times but no safe mode. Pulled each hard drive comms one at a time as I have two bootable drives. No joy.
I'm not sure where to go from here as I cant find my backup USB boot drive. (I know.. but it was 5 years ago when I installed win10). I fear its the motherboard or CPU. Any thoughts or advice? Thanks in advance.

 

[rgd1101]

before closing case I made sure all the fans on case, GPU, CPU and PSU were running.

so it wasn't beeping then?

system spec?

 

[Helpwithwindowsplease]

Motherboard : Asus H97M-E Intel H97 (Socket 1150) DDR3 MicroATX
Microprocessor: Intel Core i7-4790K 4.00 GHz (Devils Canyon) Socket LGA1150
Screens: 2 x Asus VE247H 24" Widescreen LED Multimedia Monitor
Graphics card: PowerColor AMD Radeon R9 285 2048MB GDDR5 PCI- Express
Memory: 2 x TeamGroup Xtreem LV 8GB DDR3 PC3-21300C11 2666MHz Dual Channel Kit
Keyboard: USB
Mouse: USB
PSU: SuperFlower Golden Green HX 550W "80 Plus Gold"
main disk storage: Seagate Barracuda 2TB
boot disk 1:
boot disk 2: Kingston 30GB
SSDNow S200 Drive SATA 6Gb/s 3 2.5" Solid State Hard Drive

Others things I've checked & tried:
Green power LED is lit
Removed and replaced CR battery (after 90 min wait)
Removed graphics card and used Motherboard graphic.
Removed all USB peripherals with and without keyboard & mouse

Single beep is normal on reboot from power down (i.e. windows 10 update). According to Asus beep list this is either normal or keyboard not found.
One thing I do see is drive light alongside power on light on case only flickers on once. Normally IIRC it is active during boot phase.

Thinking of removing all drives to see if it gets a response.

Most frustrating part is trying to find a sign or hint of the cause so I can fix it or at least order replacement part(s).

 

[rgd1101]

test with 1 stick of ram.

 

[Helpwithwindowsplease]

test with 1 stick of ram.

Still the same single beep with only 1 RAM in

 

[Helpwithwindowsplease]

Still the same single beep with only 1 RAM in

I bought a replacement CR2032 battery and it booted to POST screen and into BIOS. From there restored bios settings. After one false start, booted from wrong boot disk which needed sorting in BIOS its all up and running.

The first hint it was different was the numlock keyboard blinked off for a second which was the first sign it was being seen.

On a random note, found a mystery button back of machine. Turns out it switched on LED lights inside main fan. Only took me 7 years to discover it. Thanks for all of the help, it kept me going.