If it didn't happen to me I wouldn't believe it.  I moved a Dell
Dimension computer to another room to replace an Emachine that quit
working.  For convenience, I hooked up the old Emachine keyboard to the
Dell.  When I fired up the Dell, the computer beeped a few times but
nothing would appear on the monitor.  After a few hours of trying
different combinations of hardware and electrical outlets, I noticed the
system would work with no keyboard or with the original Dell keyboard.
It just wouldn't work with the Emachines keyboard.

Can anyone explain how a keyboard to stop a computer or monitor from
working?

Thanks,

Vince