I have the imac G5 17 inch with isight and about 4 months ago, I completely replaced the logic board. I believe the orginal had some busted capacitors or something. Anyway, when I initially start up my computer (after I insalled the logic board myself), the 1st thing that would happen when I turned the computer on was that a tiny little image in the center of the screen would flicker between a folder of a "mac" smily face and a question mark. After the flickering for a couple of seconds, the computer would eventually start up. Fast forward to a couple of months...I noticed that my internet explorer and firefox would freeze up after the computer was put to sleep and then woke back up. The speed of the computer started going really slow to the point where I had to shut off the computer and start it back up... Fast forward a couple of weeks ago....eventually the little image that would flicker back and forth for a few seconds at the beginning of start up would then switch to the apple logo and just sit there until the fans would start to blow. Sometimes it would switch to a white boot-up screen and I had to physically type the word "mac-boot" for the computer to start up. Eventually, it got to the point (where I am right now) where I can't even start the computer up, the fans will just blow and I have to just shut it down. I would unplug it as to reset it. but I think I'm going to have to do something maybe a bit more drastic, and I know it has to do with the switching of the logic board. It is almost like the computer doesn't recognize it's "brain" and has thus created the issue. Another thing I also noticed yesterday, as I made another attempt to turn my computer on, a circle with a cross (kinda like a "no smoking", or "Ghostbusters" logo) came up. At that point I just turned off the computer. I'm a kind of fix it myself kind of guy, for the simple fact that I like to work on computers, and that I really don't have the money to buy a new one right now. So I'm hoping as "old" as this computer is, someone has maybe experienced the same thing and maybe can advise of a solution. I think I may have to completely reboot my computer to its original settings, but I was hoping I could get on the computer one last time to back up my files that I have on the computer 1st. PLEASE HELP! Lol! I took pics, to give you a better visual! Thanks for whatever tips you can provide!