Media Live won't boot

Question

Evening!
I bought an MSI Media Live barebones back in November, it worked beautifully until a few weeks ago, as it now refuses to boot. I've disconnected everything to narrow down the cause, leaving just the PSU, motherboard and CPU. I'd be suprised if the CPU has failed (never seen one fail under normal use before), question is, is it the PSU or the motherboard? Unfortunately I don't have a spare PSU to test with, any suggestions on how I can confirm whether it works or not? I have a multimeter but don't really know how I'd use it to test. System setup (before I ripped bits out) are:
MSI Media Live barebones
Athlon 64 x2 5000+
2GB Kingston DDR2 800MHz
1.5TB Seagate HDD
XFX GT220 graphics card (plugged into the PCI-E with a flexible riser, much better than the integrated graphics!)
Cheers for any help 

Answer 1

About 10 days ago, my new MSI AIO froze up and would not boot. It wouldn't even POST - dead meat.        It turned out to be a bad memory stick. Since there were two memory sticks, it would run on the one good one until I got a replacement. So, if you have two memory sticks, try pulling each one out. If you have just the one stick, try some other memory stick. I am not above buying memory sticks from a store with an excellent return policy, just to be able to test out that possibility, and then take them back if it's not. That's what I did a year ago when I thought I'd lost the power supply when another machine wouldn't boot. It wasn't the power supply, so I took it back for a refund and ended up buying a new motherboard, which was the problem.
Bye.