Help!

I can't power up my pc. It was working fine over the weekend, but when I got home yesterday nothing. I usually leave it on, so it was weird to be off in the first place. I have other things plugged into the same power strip that come on fine.
Attempted resoloutions
I moved the cord to the wall outlet
I used another power cord
I called tech support ( ) and they were lots of help. disconnect this, now reconnect, try it again...
I came to the conclusion that it was probably the power supply. So I went to Best Buy and picked one up, switched it out and nothing...

I'm lost.......
anybody got any ideas???