My old 24 inch iMac (2008 model) will not start. Graphics card query!

Hi

My old iMac now fails to start. On pressing the start button, the screen lights up and shows an Apple logo and the progress bar appears and moves across the screen. The machine then simply restarts - again and again - before the progress bar has reached its normal finish position. Rather as described in this previous case: https://discussions.apple.com/thread/8291590

I've tried everything suggested as a solution in that particular case.

At one stage, I did manage to achieve this result:-

Neither Apple nor the local Apple Authorised dealer would look at the machine as it is now classed as 'vintage', so I took it to a local computer repair shop who said they'd inspect my machine without charge. At first they reported that the hard drive had failed and that they would replace the drive for a charge of £150, or £200 if I elected to have an SSD fitted instead.

When I baulked at the cost on this old machine, they then told me that it wasn't worth repairing anyway as they had determined that the graphics card had also failed. I subsequently removed my machine from the shop; no money was requested, nor paid.

A computer-savvy friend has suggested that there's probably nothing at all wrong with the graphics card and that replacing the hard drive is probably all that is really necessary. Now I am wondering if he's right.

So, I'd welcome the views of folk reading here too. Is there some way I can 'test' the graphics card myself?