Stunped on Dead Computer Problem!

Not long ago I went to turn on my computer and received nothing but an error on my monitor saying something about “No Sync in Horizontal Freq. No Sync in Vertical Freq.” I tried hooking up another monitor and recieved the same error message. So I preceded to change Video Card, same problem, then changed Motherboard, with its own video adapater. Same problem still. Installed new memory and now new AMD Duron CPU. Still same problem. Have even changed the power supply unit. Since the computer is all new on the inside, I am stil having the same problem, and now I am stumped. Please Help!!
I am running Windows ME, have a AMD Duron 1300ghz cpu, WD 120gig hard drive with 512 MB Ram. Thank You for any help.