HELP: power supply surgery

I got it out of the case and got all the screws out of the power supply but it still won't let me at the fan.
Jeremy wrote on :

I'm in the process of trying to replace the fan in my powersuppy G4 533 I got it out of the case and got all the screws out of the power supply but it still won't let me at the fan. there's a metal tab holding the until together. has anyone out there done this before ?

jeremy