USB keyboard doesn't work on startup "No keyboard detected!"

Have a look on the label on the underside of the keyboard, it might state the USB version type, some do and some don't, though. Your keyboard might not be USB 3 type if it is an older keyboard, might only be 1.1 as is with most keyboards pre 2006 and the motherboard might be too "new" to actually have backward compatibility as far back as USB 1.1 version. You might need to buy a new keyboard.

Back when PC's had both usb and PS2 ports for mouse and keyboard, it was often the case whereby one had to use their old PS2 (green and purple coloured connectors) to access the bios so as to enable the USB option for keyboard/mouse which is disabled by default.. Most later model motherboards have done away with the PS2 connectors relying only on USB.

Are you using a USB 3.0 port or USB 2.0? If it's 3.0, you probably don't have the drivers for it.

A motherboard doesn't have drivers, per se, just an information table pertaining to mouse and keyboard.
What make/model /serial number for the keyboard and mouse?

You may very well need a PS2 keyboard / mouse, I got a few, just in case of emergency if the usb ports fail for one reason or another, also got adapter for usb port to PS2 device and one for PS2 port to usb device.

Get a PS2 port to USB device adapter then you can use the usb keyboard (possibly), they only cost about $2.

Your keyboard is just standard model so it should work.
Try a usb port that is only 2 levels high it might have a lan port above it otherwise try the front panel usb port, if you have one.

If you have the front panel connected, you may have inadvertently put the connector back to front on the motherboard, if the front panel also does not work.

What make/model is the PSU Watts?
We also need your motherboard model and brand as well as the ram and any other hardware you have in the PC.

There are no absolute guarantees that any suggestion will work, it's all a matter of Trial and Error.
What may work for one instance may actually cause a fault in another but not in your case, though, not the usb adapter.

There have been some issues of late about mouse/keyboard and they were resolved by updating the bios. You may need to do the same.

How to update the BIOS? You'd need to go ask someone else, that is not my "expertise".

In the BIOS check for the option to ENABLE usb mouse/keyboard.

Wolfshadow said - "@TenPC, I think the question was rhetorical. How do you update the BIOS if you do not have a functioning keyboard" hmmm I suppose you are right! lol

[RANT]
Honestly, how can a motherboard have DDR3 and AMD 3+ CPU but the PCIe bus is only 16x1.
The back panel resembles something from a 2005 motherboard (or earlier).
All the USB ports are only USB 2.0 as well.
This motherboard also has 1 x COM port and 1 x Parallel port, to which were actually phased out back in 2005.
There are no printers that could utilise that parallel port (with Windows 7 or 8) unless you were using XP with a printer designed to work with XP.
[/RANT]

Basically, this motherboard has been re-commissioned to be compatible with current cpu and ram needs for those users wanting to use Windows XP operating systems. It is most likely that the motherboard does not support USB keyboard/mouse until it has been enabled in the bios, you will need PS2 mouse/keyboard.

You will need to have the PS2 keyboard and Mouse attached during installation of the OS until you get to desktop, even though you have enabled USB keyboard/mouse support in the bios. You will need SP2 (service pack 2) to enable USB 2.0 support before the USB ports can be used, they should revert to USB 1.1 standard, though.


Edit -
Storage - AMD SB710 controller :
"AMD’s SB710 is a Southbridge that integrates key I/O, communication, and audio features required in a
state-of-the-art PC into a single device. Over and beyond the features supported by the SB700, the
SB710 also supports a number of hardware monitoring features and AMD’s Advanced Clock Calibration
utility. It is specifically designed to operate with AMD’s integrated graphics processors (IGPs) and
Northbridges in desktop and mobile PCs."

http://www.tomshardware.co.uk/forum/id-1681624/information-understood-reading-pages-amd-sb710-databook.html

This motherboard is a collaboration between AMD and ASUS at a time when both manufacturers were struggling for market share back in 2006. Asus is (was) primarily Intel based chipset with Nvidia products.

You could buy an Asus Nvidia video card nowadays but you won't be able to buy an Asus AMD video card, Asus does not support AMD in that way.

Basically, even though you will get the mouse/keyboard working eventually, you may have issues with the storage controller, it being AMD and no official support drivers for it. Who would you ask? AMD or Asus?

At best, I'd say that it would be good with XP OS, plenty of updates at the motherboard site but see how you go with Windows 7 OS.
http://www.asus.com/Motherboards/M5A78LM_LX/#support_Download_30

You can't use the keyboard in the USB 3.0 port, try using a different port.

What we haven't actually confirmed is that whether the pc actually powers up!
Does the PSU turn on? Is there any display output?

Where did you acquire this motherboard?

I'd say that you should RMA the motherboard back to where you got it.

Basically, if I can't get a keyboard to work with a motherboard just to access the bios then I throw it in the bin, back to where I found it!