Any suggestions for cleaning yellowed computer parts?

Yes. Beware on this sometimes, too. I ran a Coco-3 case through the washer and it cleaned the case very well but it also washed out the colors on the label. Now, the case and label have a uniform washed out look to them. Also, I've noticed that sometimes, running a case through the dishwasher doesn't always clean thick grime off. It only bleaches it so that it looks like it's gone, and the drying heat can bake and harden the grease so that it's more difficult to remove. I still prefer to use a sink full of hot soapy water, and a medium stiff paint brush, and lots of elbow grease. The brush gets down into the cracks and crevasses, and any texturing on the case. I also prefer this method because I enjoy the act of scrubbing everything up. I like to see the cleaned piece emerge from years grime and dirt, and the work gives me time to think. A toothbrush and a facial buff pad are also useful. Short of painting, there is no way to restore a sun damaged case that I've found. I have nothing against painting an old computer case, since many of them were painted to begin with -even the plastic case were often painted.