Your laptop may have a single fan with a Xbox360 like combined heatsink for the cpu and gpu depending on the design, either you need to use speedfan or a similar utility, bios fan speed tweaking if supported or it may be non adjustable, and preset based on temps.
edit: The G73 has 2 fans for the CPU and GPU located on the far left and right sides of the chassis, but it is still non adjustable and clocks automatically based on temps I believe. I have a G51 and I know my fan cannot be manually controlled, well at least not easily and not without hex editing on the motherboard and even then it's only temporary. I use RW Utility to manually edit the code in the electronic Controller chip. The simplest write switches fanspeeds permanently for about 3 seconds until it auto-corrects, but now I have a saved config that sets fanspeeds to 100% until reeboot, at which time I need to reload the .rw file to set fanspeeds up again.