Okay guys, no one will probably ever find this useful, but I had to write it... (With added humor) How to Correctly Replace the Power Supply in a Dell Dimension 9150 Desktop Computer. Required Tools Phillips-tipped Screwdriver Room capable of suppressing the sound of you yelling WTF!!! Removing Existing Power Supply Turn off computer.. This is a requirement. Remove all external cables connected to computer, including power cable. Press power button (This will ground the motherboard after power cable was unplugged). Press it several more times as this is the most fun you are going to have during this procedure. Lay computer on side (no, the other side, it's a Dell), pull lever on top of case to release side panel and remove it. Admire the wonderful cable management they've done (it is very well done!). This is also going to be your first clue that this will be a little more work than you had imagined. Unplug power cables from motherboard and all drives. Many are hard to reach. You may require bandages after this step. At this point you will realize that Dell covers the CPU cooler and the fan for the cooler with plastic shrouds that direct the airflow out of the case. IMO, this is a good idea. However, you will also realize that the power supply harness runs under the CPU shroud and that you will have to tilt the shroud out of the way to access the cable. No big deal, right? This is were things take a turn to the bizarre. After inspecting the shroud, you will come to the additional realization that the shroud and the CPU cooler are one assembly, meaning that you will have to remove the CPU cooler from the CPU in order to remove the power supply harness. This is the first instance for the need of the second line item under “Required Tools”. This is also why you removed all external cables, as at this point you may be lifting the unit up to pitch it out the window. This also adds another item to the list … 1/4” Nut driver with at least 5” shaft. To unbolt shroud. You will now find that Dell puts some type of melted crap on the bolts so they can tell if you fiddled with it. Of course, the nut driver will not go over the bolts. Use a sharp instrument (like an ice pick) to break apart the crap. Don't bother being careful, destroying the motherboard would save you a lot of hassle at this point. Once the CPU cooler is removed, you can easily remove the harness … except that you cannot get your hands into the area where the harness is clipped to the bottom side of the case. Simply use a flat-tipped screwdriver or knife to unhook the latches. Optionally, you can just cut the clips apart, using a side cutters, knife or chainsaw(preferred), as you will never use them again if you are smart. Continuing on …. Unbolt shroud and remove. You will be surprised that Dell actually used thermal compound on the CPU and not a thermal pad. Remove the harness. Unscrew the 4 screws holding the power supply into the case. Depress the tab underneath the power supply and slide it back about an inch and remove it You have now successfully removed the power supply from your Dell 9150. Congratulations! Installing the New Power Supply What every good system builder does before installing a power supply is to ensure that the cables on the new one will reach their intended destinations. You will immediately realize that no one on this planet makes a supply that has long enough cables to route the way that Dell does it. You have two options here, either start yelling and throwing stuff, or realize that this is a Godsend as no one in their right mind would re-route the cables back under the shroud in case they ever had to remove it again. Slide new power supply into place and put the 4 screws in to hold it in the case. You have now figured out that the Dell power supply is about ½ inch wider than a standard one, and that there is a air gap just below the new supply. Forget about it !! It's not worth it. Just screw the stupid thing into the case. You will thank me for that suggestion. Clean thermal compound off of CPU and cooler. I used a old napkin and alcohol.. Who cares. At this point I just want the blasted thing back together. Re-apply compound. Being careful not to use too much is optional. Put cooler back on CPU and tighten down bolts. Don't bother checking for good spread. Currently you can only hope that the CPU will burn out and you can build a real rig. Plug everything back in, routing the cables on top. No worries, it's a Dell. You can't see inside it anyway. Cram left over cables anywhere they will fit. If you are worried about airfow, re-read last sentence of #3 above. Put side cover back on. Maybe with a little luck you will pinch a cable and everything will short out. One can dream, can't one? Plug external cables back in and fire it up. Pray for smoke and/or flames. Success !! Everything works (at least for me it did). Congratulate yourself, and next time build your own rig right from the start.