|Did you buy them directly from Gateway? |
Are both PCs connected to the same wall outlet or power strip? If they aren't, swap them.
Anytime I had that problem, it was either the power supply or the motherboard. When it was the motherboard, there was a click & a really fast shutdown.
Also make sure that both fans are spinning, the one in the power supply & the one near the CPU.
How do you know when a politician is lying? His mouth is moving.