HELP REQ: imac G5 not loading!

Hi,

I have an iMac G5 that has worked okay - bit sluggish recently but I think that was a widget I got rid of!

Anyway just the other day updated leopard (combined update) on software update - worked fine next day but then the next day wouldn't load - getting stuck on spinny circle, grey splash screen with apple.

I have tried to enter in T mode (firewire) and I can access the hard disk fine, I have tried resetting PRAM/SMU using the old hold down certain keys on boot and this resulted in the fan kicking in but not a lot else, I then tried holding c to bot from CD or alt to boot into disk repair BUT the DVD just spins around and then pops back out - impossible to access it at all!

I tried bootting in verbose? mode to see error messages and there was loads of errors to do with i/o.

Nothing hardware wise has been changed on the imac and it has worked for ages - I feel I have tried all the usual ways to get round it but I cannot get in to reinstall or backpedal with timemachine!

Any help appreciated.

Thanks,

Peter