newly built pc shuts off seconds after powering it on.

Hello. I just put together my first p.c. kind of a low budget job . K8N Neo3 Series MS-7135 (v2.X) ATX Mainboard, and a AMD MOBILE 3200+ (2.0 GHz) 1MB 754 SOCKET. also 2GB (2x1GB) PC3200 DDR400 MEMORY and a NEW Seagate 400GB ATA Internal Hard Drive . the video card is a cheap SAPPHIRE ATI RADEON X1550 512MB PCI-Express . my Q is when I power on the pc it shuts off after a couple of secs. no beeps . if I take the ram out it stays on but still no beeps and nothing on the moniter. could it be the cpu? any direction would be helpfull thanks.