power source problems?

I put together a brand new computer with new parts. I was too cheap to buy a power source so i thought a 300W psu would be enough. I found out it wasn't so i got a 350W PSU and it was working fine for a week or two. Now when i try to power up, the heatsink fan and the psu fan powers up, but no picture on the monitor, keyboard and mouse doesn't work (they don't light up at the initial start up). The dvd rom and cd burner lights up and it seems like the hard drive is working too. Now I'm not sure exactly what's causing it not all to work, keyboard, mouse, and monitor, but is it becaues i don't have enough power?

thanks

It sounds like your motherboard power connector may just be loose or not fully seated. Recheck it.

that's not the problem...i have it all connected and i checked it like a billion times. what else could it be?

It might not even by your power supply. See if you can get your hands on another power supply and retest the system. If it works with the new power supply, you know what the problem is. If it doesn't, you'll have to look elsewhere.

hmmm ive had that happen to my pc becuase i kept moving the parts around, try taking all hardware out and placing back in or reset your bios. swap ram slots.