Motherboard dead or power supply?

[SandraTrying]

Just to let everyone know first, I'm not very techy/good at this stuff. I know several things but I'm far from good haha.
So my problem:
Every time I turn on the power for my computer the fans run but the light on the power button blinks once and then stays off. I have to try several times to hold the button/turn it off and then try turning it on again before it totally starts. I'm wondering if this is just a power supply problem or a motherboard issue? I've got an Acer Aspire AX3400-E2202 AMD Athlon IIX2 215 dual-core processor.
Also, if I were to get a new power supply unit would I have to stick to the watts of what it is now or could I move up to something like 300?

Thanks in advance

 

[Tmagic650]

Yes try a new power supply first... 350 to 500 watts is okay

 

[mike1959]

Changing PSU

It might sound obvious, but it would be a good idea to take a few photo's of the whole PC motherboard, and some close-up's also, so that you plug all the wiring into the right places.
It's REALLY EASY to leave a plug out when re-building a board, and not to be able to remember what it was like before.
Look at the main power connector onto the motherboard, it is made up of a long plug AND a small plug. It's very easy to forget to plug the smaller one in, and the PC will not run, of course.