Thanks so much for the above post/s, was having the power light come on my G5 1.8Ghz with 2G of ram but that's as far as it went with no screen appearing at all. Ordered & installed replacement battery, which made no difference. Like the post by P.B above I have just removed some of the RAM (but i left matching 512mb's in the top slot of the top 2 and the bottom of the bottom 2) It has fired up first time and I'm now backing up irreplaceable files i thought may have been lost. The fan is pretty noisy now but even if it only works for the next 2 hours i'm grateful,thanks again !