Help! Built Computers Will Power Up But Not Post

[klop]

I have three self-built computers which will power up right now but not post. Two of these computers were working previously, but were bumped and then stopped working. The other is a new computer. I have stripped them down to just a power supply (which has been tested to verify that it works), a motherboard, a CPU, a heatsink, a fan, and the speaker. The system powers up - fans turn on, lights on motherboard turn on, hard drives click if connected- but no post occurs. Any help would certainly be appreciated.

[hockey man]

Any beeps? And Welcome to the Pc Guide.

[Whyzman]

but were bumpedBumped as in "T-Boned" by a semi, dropped off a dolly, or slightly hip-checked?

Indeed, any beeps? You might want to try a stick of RAM also...

[klop]

There are no beeps.

One was slightly joggled when putting in a cable; the other was kicked, but didn't fall over.

I have tried a stick of RAM, but no POST occurs.

[ski]

Also, if the MB's do not have onboard video adapters, then are video cards installed?
And what about KB's?