Re: Replacement power supply for Dell Dimension 9150
After my second Dell PSU failed I bought a Seasonic SS-520GB (520W) PSU. I am very pleased with it. It has a power switch and plenty of leads, and is very quiet and stable. You need to snap off a metal tab from the 9150 case to fit it in but that's no big deal.
You can buy a Corsair and other brands cheaper but I read people had problems with them.
The Dimension 9150 manual shows you how to remove the CPU heat sink so as to clean the CPU fan. Otherwise, better not to touch it...