The problem is this;

I have a bondi blue Imac G3 DV.

I was trying to install OSX Panther, upgrading from OS9. I had clicked on the install Icon and it looked as if it was installing - with a little rotating graphic.
Nothing else happened for 4 hours or so, and eventually I pressed the restart button.
Since then the machine does very little. It sounds as if it's going to start up, but only for about 10 seconds. The screen remains black, and the CD drive goes round for 3 seconds or so, before the whole thing switches off after about 10 seconds.

Obviously there is a serious problem, but is there anything I can do to sort it out?

I have been told that Norton Utilities may be the answer - is it worth spending the money, or is there something else I should try. I got the computer second hand, and the install disk that came with it has a crack in it. Someone else has told me that the logic board may need replacing... all the options involve expenditure, so I need advice on which to spend money on.

Any suggestions gratefully recieved.