You need a specific Dell one
Dell are cunts and the power connector that goes from the PSU to the PCB motherboard is a non standard connector pinout, or at least it is on my PE540.
( turb0t, Sun 14 Jun 2009, 22:06, archived)

ok thats no problem
there is a dell reseller literally opposite
(El Guiri the only b3tan who is not fat, Sun 14 Jun 2009, 22:12, archived)