Several years ago I bought a dell dimension, and I've gotten by since with upgrading my gfx card, until it fried on me. My psu was max 250 W, so I tried to upgrade that as well (newegg had a good combo deal with the card i bought) anyway I unplugged the old psu, hooked up the new one. I turned it on, and no beeps, no display output, one of the power leds was yellow. I turned it off and back on again, everything seemed fine but still no display output and no beeps, though I could hear the hard drives spinning. I took out the new psu and put in the old one, hooked everythign back up, but still nothing. I tested it using an old gfx card that still works. I think I might have fried the mobo, as one of the mobo's heatsinks now gets burningly hot if I even attempt to turn on the computer, regardless of which psu I use. my new psu is 650 W max, but it came with the correct connector (20 pin main, 4 pin cpu) and the voltages seemed to be the same as my old one. Did i fry it? A friend told me afterwards that if you hook up a non-dell psu to a dell mobo, it will kill it, and the mobo is rather old (4 years)...