You never ever swap cables between PSUs. It's not a Dell thing - you must use the cables that ship with the PSU. Many people have fried their mainboard like you.
You're talking about something different. In the early 2000s, before modular PSU cables, Dell used non-standard PSU power connector wiring arrangements. The 20-pin mobo power plug coming out of the PSU was wired differently than the ATX standard at the time, and swapping hardware could fry a motherboard.
Yeah, I wasn't "swapping" PSU cables; the cable was part of the PSU. I replaced a Dell PSU with a standard one, and <smoke!> No more motherboard.
Manufacturers who pull this type of incompatibility shit risk their reputation. I never went near anything with a Dell label again until last year, when I bought a second-hand laptop (I don't attempt laptop upgrades and repairs).
