OK, I'm going to close this thread. Many thanks for all your help/suggestions. Just a couple of things to mention. The desktop drive I tried to test using the USB adapter - it does need an external power supply and I didn't know that at the time. I did connect it to my desktop using the internal connectors and still could not read the disk so that pretty much tells me the disk is one problem. Regarding the blank screen, as one of you said, it's either the mobo or video. In this all-in-one, I believe the video is integrated with the processor as I have taken the thing apart and cannot spot any separate video card. I didn't mention this before but I am trying to fix this computer for a friend and, since I don't have all the electronic gizmos that repair shops have, I can't nail down the specific problem and, as a result, I've told her that it's not worth fixing. It's close on 10 years old and new or even used mobos don't seem to be available in the UK and if it's the video, then a new processor is required. More expense than it's worth. Having said all that, I've learned a lot from your posts and for that I'm grateful. Thank you all very much.