BleepingComputer.com: computer will not power on

so this is in regards to my moms dell dimension e510 desktop..it has win xp..was bought new in nov' 05

she texts me this morning to say her computer "blew up"..i go over..nothing is smoking..so i assume she's crazy..i make sure everything is plugged in firmly, etc..nothing happens..the wall outlet seems to be fine as well..so i take her tower home with me and tell her i'll take a look (not really knowing what i'm gonna "look" for)

so, i get it home and think maybe her power supply just sucks..so i find a spare..and TA DA!! the tower powers up...so then i unplug it and reinsert HER power supply and nothing happens..so i figure, eh..that was easy..

then i plug MY power supply back in..and...nothing. at. all. (then i plugged and unplugged it a dozen more times for posterity..nothing happens)

i took the side cover off and made sure everything was seated properly (seemed like a good idea?)..i tried the power button and noticed it flashes yellow if i hold it in..so i assumed that the power button IS working..

and thats where i'm at..

is it the motherboard..is it the blankity blank..the hoosenhoffer...?

please help!

Did you try her PSU in your system?

Did you try turning the PSU off at its switch...and then turning it back on, before pressing the system Power button?

Are the fans spinning?

Louis