PC turned off unexpectedly

My tower is on the floor under the desk, near my knee. But not close enough that I would knock into it- except for tonight.
I accidentley hit (not too hard) my knee to the tower and the tower turned off. Some thing is loose- but what would I be looking for?
Power supply connection? or ... ?

Check all connections to the tower as having a keyboard or mouse unattached can cause issues as well as having the power cable come loose. After verifying all connections are solid, try to turn the computer on and let us know what happens, if anything

All cables connected to the exterior are seated securley.
Tried to replicate the power loss and of course could not.
Besides the power supply - what else should I be looking for inside ?
Thx

Possibly something on the inside that might be shorting the power? If you know how to open your tower, power it down, disconnect the power cord, open it and look for loose cables or wires.

Well have not been able to replicate another shut down - which is good.

So you mean now you are intentionally kicking your tower to check if its shutdown.. LOL

I am find the I am kicking the tower less then when I had XP.
And Vista was not bad- I found that better than XP and Win 7 is even better.

Never kicked the tower, but I did kick my UPS a couple of times!