Faulty motherboard?

I've got a Gigabyte H81N. A few weeks ago I came to my PC and it wouldn't turn on. I assumed the PSU had gone since there was nothing happening at all, not even the fans wanting to spin.

I picked up a new PSU and the board fired right up and has been running fine since. I left the PC on overnight, and this morning found it was off. Again it won't start.

I've stripped everything bar the CPU/cooler from the board, and plugged in the PSU connectors. If I jump the power switch the CPU fan will spin for a split second, then stop. Same deal when I jump the CMOS reset.

I'm doubting this is two PSU failure in a few weeks considering I've not had any for about 5 years.

Any thoughts?

what new PSU did you buy to replace the old one?

brand?
Model?

Well I replaced the case inc the psu. It's an antec ISK-300 with 150w PSU, which is plenty for the my components. Pentium G3420, onboard graphics, 8gb ram.

I would say get a stronger PSU, the thing with PSU's that come with cases is they are all made to fit a budget, and that includes the PSU. in the worst case's when they die they also take other parts of your PC with them.

It's a discrete HTPC it's suppose to have a low wattage PSU. Many people use pico type psus and just 120w power bricks. I was previously running a 120w psu for 3 years.

The psu's that Antec package with their cases are generally good units. At one time they came with the Earthwatts psu's which were very good for budget units. The 150w unit that comes with the ISK300 is also a decent unit and is specially designed for the case. There's a review of it here and the biggest problem with it is efficiency but it can deliver the power it's supposed to. You can't just stick any psu in the ISK300 as they wouldn't fit. It easily has more power then the ops pc will ever need. My wifes pc is a similar spec and rarely hits 50w at the wall with her usage.