Further to all the above, I took the advice and got him a new system (at great expense), which has been great so far, UNTIL NOW!.

He just finished downloading the latest GTA for PC edition, which took him (with our rubbish broadband signal) 12 days to complete. (59GB), having checked all the system requirements first to make sure we didn't get any problems with size etc.

So, apparently when he started playing it was fine apart from some of the graphics were showing grey pieces. Having gone to the game settings screen, I just saw that the "graphics" setting in the menu is VIDEO MEMORY 964/768mb and has a long red line to the right of it.
Not knowing much about these things, I don't know what this means, but suspect that the red line means it maybe needs this amount to function. If so I am now totally confused, as I have tried various blogs etc to find out how to find the video memory for this PC and ended up with the APPROX TOTAL MEMORY 4095mb, which surely should be enough to supply the above.

Hence I need some brilliant expert which I am sure is here somewhere, to help me try solve this before he comes home from school so I can cheer him up and get rid of his total disappointment.

Any help in simple language, would be really appreciated.

John