Can’t get past Splash Screen

Hi gang,
I have a 2 year old Gateway that initally had trouble finding the hard drive at boot up. Cutsomer thought it was the HDD, but once I disable PXE boot, it found the hard drive and ran fine for 3 months. Recently they contacted me again and reported the “same thing” was happening. This time it’s rather different, in that it will load as far as the Gateway splash screen with the BIOS options. For about 20 seconds the keyboard is responsive, and then it too locks up.

I have swapped out every swappable part (RAM, HDD) I have even replaced the motherboard, so there is a new CPU.

I’m just banging my head on a wall… does anyone have a clue or sugestion to get me on the right track?

Thanks.