How can I determine which PSU will be a clean retro-fit in my HP p6100z desk top? Th existing 300 w PSU is Bestec model A3X0300DSWCREVA.
Your current Bestec ATX0300D5WC Rev A power supply is a standard ATX12V form factor power supply unit with dimensions 5.9" W x 3.39" H x 5.51" D.
Are you upgrading the power supply because you've purchased a new graphics card? If yes, please specify the make and model of the new graphics card.