MacBook white 13" 2.2 GHz with 4 GB RAM and 250 GB HDD. I've been watching a lot of YouTube lately and noticed my fan whirring a lot. A lot of heat under the 1-2-3 keys has caused the white plastic on the underside to yellow a bit (2" diameter) and a little bit of chipping of the white finish (1/2" diameter). Computer works fine when cold, but once warmed up, the sound controls become erratic and then there is no sound, but everything else works ok. Turn it off for a while and it's fine again when turned on, but only for a short while. Any idea what's wrong? If repairs are not cost effective, is there any monetary resale value for such a machine?