I had the same problem with the G74sx , it drove me mad , i was literary 2 meters away from my wireless router and i still got a crappy reception.
I'm not sure if it would work with your model though.
What i did is i went to the 'device manager' through 'my computer' and uninstalled the wifi driver , then i right clicked and selected , 'scan for new hardware changes' , the driver reinstalled itself and that fixed my problem. Full bars of wifi now.
I hope this helps.
Asus G74SX-TY087V
Processor: Intel Core i7 2630QM / 2 GHz ( Quad-Core )
RAM: 16 GB - DDR3 SDRAM
Card Reader: 3 in 1
Hard Drive: 1.0 TB - Serial ATA-300 - 7200 rpm
Optical Storage: DVD-Writer / BD-ROM
Display: 17.3" LED backlight TFT 1600 x 900 - 16:9
Graphics Controller: NVIDIA GeForce GTX 560M
Video Memory: 3 GB GDDR5 SDRAM
ConsolesPlaystation 3
Nintendo Wii