How long have you had your G73sw? If you've had it for a year plus.. then blowing it with compressed air isn't going to help, mainly because there are probably already several layers of dust build up on the heatsinks. I'd suggest that you take it a part and clean out the inside of the chassis and fan for dust.
If it is all of a sudden getting very hot, that is a sign that the thermal compound has just dried up.. it is the paste that goes is squeezed between the processor/graphics card and the heatsink.
If you do plan to do a repaste on the thermal compound, you can get some for $10+, get 3rd part thermal compound such as Arctic Silver.
For applying it, the easiest way to do it is to squeeze a rice sized drop on the center of the processor (and gpu), and allow the evenly pressured push of the heatsink onto the component make the compound spread to all corners of the chip. (whipe off excess).
Hope this helps,
G.I. JOE out.
