I built a new machine (with help from a tech friend) about two years ago, new motherboard, cpu etc ... I reused my old HP monitor, keyboard and mouse and had no problems until about six months ago.
The computer powers up fine and everything is going but the mouse and keyboard are sometimes not working. The keyboard comes up with all three lights going but you are unable to key. The mouse will be frozen. Mostly the keyboard fault occurs but sometimes after powering down and checking the connection the keyboard will be ok on startup but the mouse not working.
This doesn't happen ALL the time - very intermittantly.. but it seems to becoming more frequent. It usually fixes itself - I found shutting off the computer and restarting until they are working is the only way. This works even without checking the connections - which is weird.
The other thing is my usb ports can show power lights (camera etc) but the computer isn't recognising the usb as an extra drive.
Could this be a motherboard fault?
Appreciate any advice.. don't really want to take it into a shop and find that I should have just bought a new mouse/keyboard!

You're not likely to get an answer to a question in the Community Introductions forum. Might I suggest the Hardware->Peripherals forum? Before posting, it's a good idea to find the most relevant forum for your post.

Moving to the appropriate forum now...

Thanks for the hint - new to this! When I did it I thought I was in the right one but it came up with log in again and I didn't check again... duh!

I guess they're all USB devices?
If so (and especially if they're connected through a USB hub) you may have power problems.
If you can't get enough electrical power to the devices (many unpowered USB hubs have that problem when they're full) some or all may fail.