I kinda hate to say this, but you probably need a new machine. You can browse ebay and see if you can score a model like yours for the right price, swap HD's and go from there. Maybe it'll last a few years. I've found out that much of the time it is far easier (and cheaper) to replace rather than repair. If you can sell your old machine for parts then all the better. I have a model like yours, tried all these suggestions and no results. I looked inside to see how much trouble I'd get into replacing the logic board and possibly the processors and come to the conclusion that Apple does not want you to repair them. So, I found one like mine on ebay for around $200 and hopefully I can just swap HD's, like I mentioned. Sine the introduction of the intel models these older PPC's art getting much cheaper. Anyway good luck, hopefully your issues can be settled easily.