I posted this problem (below) on Monday and have reset the pram and the SMU by unplugging from the wall, as yet have not opened her up. Working with her all week the problem only occurs when she is idle, she goes to sleep and will not come back up. I put her into sleep mode myself and tried to bring her back straight away even before the fans got loud but she would not come back. So it now seems that my main problem is if the mac is idle it will not come back up without a retstart. Been in touch with a support place who say the hard disc is failing and it needs a new hard disc, reluctant to do that but it now looks it may be the time to update. Anyone else come across this I bought this Mac in 2005 and am told I may get £100 quid for it! My spec is 2.3GHz Power PC G5 Mac OSX Vers 10.4.11. 4.5 GB RAM Over the weekend I got back from a weeks holiday and powered up my Mac. On three occasions yesterday while it was left alone or in sleep mode the fans went very loud and the screen would not come back up. The only way to stop the fans was to hold in the start button for several seconds until it powered down and restart it up again.