"I have an Intel 24" Imac (late 2008) that was giving me lots of problems although it worked fine if I used a second external monitor. "

But at that point you didn't reveal if you had that issue fixed. I'm guessing you did not and now want to start a career in PC repair. Since the power support can be swapped out and may be the cheap part you are following some one's sage advice. Try the cheap parts first.