Dell gets a huge thumbs down for shipping proprietary ATX PSUs with the _standard_ ATX connector, but different wiring.
proprietary PSUs and a ready made adapter.
While the link above details how you can manually convert a standard ATX PSU to work with a Dell mainboard, it’s ridiculous that one would need to take such action.
Based on this, I cannot and will not recommend Dell systems to anyone until this nonsense is resolved.
(More conversion links if that’s your thing.)
Update 1st June, 2004: I purchased an adapter from Silicon Acoustics. It works fine and I’m using my old Dell P3 mainboard with a standard ATX power supply now without issue. It was quite inexpensive compared to the cost of a new mainboard, CPU, RAM, and so forth.