Board:
ASUS P8H61-M LE-CSM, 16GB DDR3, i3 3.1GHz (original BIOS)
 
Internal Drives:
SanDisk SDSSDXPS480G
Crucial CT240M500SSD1
WD WD5000AVDS-63U7B1
 
External drive:
WD My Book 1140
 
Video:
AMD Radeon HD 7700
 
Audio is an M-Audio M-Track Quad on USB. I have printers and a scanner connected by USB, but not drawing power. I have a 550W power supply. The system and peripherals are supported by UPS.
 
Windows 10 64bit.
 
When I first built the box, it booted at lightning speed. Anything and everything I connected was fine. For a few months now, I have noticed slower and slower booting. Sometimes it will give 5 beeps. Often, the HD light will come on at power-on, and be continuous through the boot, then last for a while afterward. In these events, the internal 500GB WD drive will not be recognized. I have been able to swap cables and make it discoverable, or just disconnect and reconnect, but sometimes even this doesn't work. The occasions when it is just discovered without extra effort are rare.
 
More background on that drive, this is a replacement for a previous drive which had the same issues, but also developed extensive errors. I'm thinking now that this disappearing act means my motherboard is going tits-up.
 
I've done 3rd party virus scans, and regularly use Malwarebytes. Windows Defender is in place, and I do all the updates Windows wants.
 
Ideas?

Look up the BIOS code for 5 beeps.  Also update our BIOS.

kitekrazy1
Look up the BIOS code for 5 beeps.  Also update our BIOS.

The nearest I could find regarding this board is the video card might have an issue. Updating the bios should be done before installing an OS, shouldn't it? Risky at this point.
 
In relation to the beep(s) during POST, sometimes there is no beep and no startup. It just stays in POST. A reset will get it to start.

pencilartist

kitekrazy1
Look up the BIOS code for 5 beeps.  Also update our BIOS.

The nearest I could find regarding this board is the video card might have an issue. Updating the bios should be done before installing an OS, shouldn't it? Risky at this point.
 
In relation to the beep(s) during POST, sometimes there is no beep and no startup. It just stays in POST. A reset will get it to start.

BIOS are only risky if there's a power outage while updating.  Replace the video card with something under $50.
 

kitekrazy1

pencilartist

kitekrazy1
Look up the BIOS code for 5 beeps.  Also update our BIOS.

The nearest I could find regarding this board is the video card might have an issue. Updating the bios should be done before installing an OS, shouldn't it? Risky at this point.
 
In relation to the beep(s) during POST, sometimes there is no beep and no startup. It just stays in POST. A reset will get it to start.

BIOS are only risky if there's a power outage while updating.  Replace the video card with something under $50.
 

I understand about the BIOS and power, but what do you have against my video card?
 
I'm searching in vain for a ROM BIOS for this board. There is only the Flashback version (P8H61-M-LE-CSM-R2-ASUS-1414.CAP), and this board doesn't support Flashback. Now I remember why I left the BIOS as-is.

A few suggestions:
1) Capacitors going bad is quite common.  Visually inspect the motherboard and identify the caps (They resemble small barrels).  The tops should be flat or concave.  If they're bulging even a little (Or worse, have burst and are leaking) then there's your answer. 
 
2) This tip, when described, seems like it wouldn't work, but I've personally seen it fix a "possessed" PC on two occasions:  Unplug the AC cord or turn off the power supply switch on the back.  Press the PC's power button and hold it in for 5 seconds.  This drains all the residual power from the board (which causes the wonky behavior).  Plug back in, power up and see what happens.
 
3)  Does your motherboard have a built-in video card?  If so, temporarily remove the HD 7700 and switch over to the onboard graphics.  This will confirm/rule out if the 7700 is the culprit.

JonD
A few suggestions:
1) Capacitors going bad is quite common.  Visually inspect the motherboard and identify the caps (They resemble small barrels).  The tops should be flat or concave.  If they're bulging even a little (Or worse, have burst and are leaking) then there's your answer. 
 
2) This tip, when described, seems like it wouldn't work, but I've personally seen it fix a "possessed" PC on two occasions:  Unplug the AC cord or turn off the power supply switch on the back.  Press the PC's power button and hold it in for 5 seconds.  This drains all the residual power from the board (which causes the wonky behavior).  Plug back in, power up and see what happens.
 
3)  Does your motherboard have a built-in video card?  If so, temporarily remove the HD 7700 and switch over to the onboard graphics.  This will confirm/rule out if the 7700 is the culprit.

I will try the onboard video and see. I've done the power drain before, but didn't notice anything changing.
 
I've also browsed the Event Viewer to see what Windows thinks is happening. Sometimes there is a failed driver for my Wacom tablet shortly before a reboot happens (yes, I've been seeing unexpected reboots, too). No mention of the video card, however, has made its way to the report. Maybe I will uninstall the tablet and see what develops.
 
I'll take a closer look at the caps, too. I've replaced them on vintage circuit boards before, but I won't try it in this one.

https://www.asus.com/Moth...ds/P8H61M_LE/HelpDesk/

kitekrazy1
https://www.asus.com/Moth...ds/P8H61M_LE/HelpDesk/

Thank you, but I've already been there. The only BIOS to be had can't be used on this motherboard.

If...a big if, you can find the disk that came with the mobo, you could attempt to reload bios from that.