I got this old MacBook Pro (Early 2006) with a ATi Mobility Radeon X1600. At times it would display all kind of graphics glitches on the display. At other times it wouldn’t boot at all.
I knew it was a hardware problem, and googling around I found that some crazy guys got it back working by taking the logic board (that’s how Apple calls the main board) out and putting it in the oven. The explanation was that the heat would allow the BGA soldering to reflow. This hardware was made some time after new industry regulations required lead-free soldering. Apparently the processes for the new materials were not perfect yet, so a lot of hardware made around 2006 had this problem.
I had to do this my way. The concept is the same I read on the forums, expose the logic board to a high temperature (near to solder melting point). An oven seems perfect for this job, but regrettably mine has not a good temperature control (how do I know? I should post more about my kitchen adventures!). So I switched the oven to grill mode (what fellow Americans call broiler), covered the whole board except the interested part in tin foil, and made my own thermometer. I put a little piece of solder at about the same distance from the heating unit as the board, and watched as it melted. When it was completely melted I knew the GPU was resoldering.
And voilà. The board was back alive. No more glitches, all graphics were working as intended! Do this at home!