Computer Stopped Operating

by James
(USA)

I have an E machine T 3985 and it quit running and the
power light would not come on. I disconnected all drives, still no power except one small green LED on the motherboard. I tried 3 power supplies with no luck, so replaced the motherboard with exact replacement Intel D865GVHZ.

Now when I plug in the power cord, all fans run and the monitor has a square in the center approx 3" with some tiny icons in it. There is no curser or writing and the power switch will not turn the machine off. It has to be unplugged. Any ideas?

Thanks.