Dell 305W Power Supply Model H305N-00 in perfect working condition.
This is from my Dell Dimension E510 (also marketed as Dell 5150) which I have finally retired.
The same power supply is used in the following Dell minitowers (and probably more):
Dimension E310, E510, E520, E521,3100,5100, 5150Optiplex 740, 745, 755, GX320, GX520, GX620
Just to make sure, take a look at the photos of the connectors and the label.