I recently ACQUIRED a Dell Optiplex GX620 desktop computer with a Pentium 4 HT CPU. It came without a power supply. I also have another Dell computer, an Optiplex GX270 in a small form factor with a working power supply. The power supply connector from the SFF Dell GX270 seems to fit fine into the motherboard connector on the GX 620 desktop. Although the case of the power supply won't fit properly for a permanent installation, I'd just like to USE it to test the desktop computer. Is the power supply from the SFF compatible with the motherboard on the desktop computer, or am I risking frying my motherboard with the wrong power supply? Thanks in advance for all assistance.I have done this before when mixing dead systems to make a good working computer. The SFF power supply though is rated a lesser wattage usually than desktop computers, so installing a beefy video card may be too much for it. But if you are going to run it simply with a single hard drive, and integrated video it will work fine. If you want to use a video card in it, you might be pushing the power supply to its limit.

The last tower that I installed a SFF power supply into to get by was an ugly working computer, but it worked. I essentially had the SFF long rectangular power supply protruding out of the rear cut out that a NORMAL square box type PSU would mount and had lots of duct tape inside to affix the SFF PSU to the inside chasis of the computer.

* But power supplies are cheap and most universal 300-450watt power supplies would fit. The only CATCH would be if the mounting holes are non universal on the case. I know that some HP/Compaq's have a PSU compartment that looks liek it will take a universal power supply and then you go to screw the power supply in with 4 screws and only 1 screw will line up and the 3 others are not universal drilled mounting pattern. ( I have had to make a stencil and drill out Compaq and HP cases to accept universal power supplies and get the 4 screws to mount the supply! )

I am actually using a DELL Pentium 4 power supply from an OLD Dell Pentium 4 tower in a universal case as the PSU for a Server with a Sempron 145 CPU and it works well, so I know at least the Dell that this PSU came out of was a universal PSU case and of the same time period of your computer.

* If you can afford $25 for a power supply, I'd go the route of installing a PSU other than the SFF PSU, but if you dont want to spend money the SFF PSU will be fine under light power demands, but would not work well if used in a computer intended of gaming with a video card beyond the demands of a GeForce 4. (* I had a GeForce 4 MX 440 with 64MB video RAM which was PCI type when there was AGP and PCI cards about 10 years ago, and it was installed into a HP EVO SFF 1.5Ghz P4 and it worked ok with half-height bracket. )Thanks for a very detailed and helpful reply!