Computer won’t start

My computer was running fine until recently. I left my computer on to go to school, and when I came back I found the computer running with the lights on, but nothing on my monitor. When I tried to restart my computer, I found that the power LED and the fans would turn on, but the computer would not post. There are no beeps either. When I looked at the motherboard, I found that the memory LED does not come on, and my video card fan was not running. Could this be a problem with the motherboard? My system is:

AMD Athlon XP 2600+
Gigabyte GA-7VT600-L
1 GB DDR PC3200 PQI Ram
GeForce 6600GT
500W Power Supply