Chosen Solution
As the title says, when I try and boot into a starup manager to install a MacOS on a new HDD I put into an iMac it only shows white screen with cursor on it with nothing else on the screen. Any help is welcome, thanks in advance.
So that tells us the onboard GPU has failed! Most likely you have the NVIDIA GeForce 9400M. You’ll need a new logic board with this version 21.5” iMac Logic Board, 3.06GHz, NVIDIA If you have the ATI Radeon HD 4670 model, you’re in luck! As this version has the MXM graphics board 21.5” iMac ATI Radeon HD 4670 GPU board
