Computer won’t start

My Computer:
AMD 900Mhz
128MB RAM
CDRW
CD 52x
32MB Prophet II Video
1? years old… just out of warranty

My computer decided to not start recently. Both fans on the power supply and CPU work, and there’s a red light on the motherboard. Before this happened, I would have lock up problems running multimedia, which i never had before. Could it just be the RAM that failed, or am I looking at having to replace the motherboard?