Apple Mac mini (Intel-based; Mid 2007) - Manual (Page 39)

Chapter 3 Problem, Meet Solution 39
Problems with AirPort Extreme Wireless Communication
If you have trouble using AirPort Extreme wireless communication
 Make sure the computer or network you are trying to connect to is running and has a
wireless access point.
 Make sure you have properly configured the software according to the instructions
that came with your base station or access point.
 Make sure you are within antenna range of the other computer or the network’s
access point. Nearby electronic devices or metal structures can interfere with wireless
communication and reduce this range. Repositioning or rotating the computer might
improve reception.
 Check the AirPort (Z) status menu in the menu bar. Up to four bars appear,
indicating signal strength. If you don’t see the bars, try moving your location.
 See AirPort Help (choose Help > Mac Help, and then choose Library > AirPort Help
from the menu bar). Also see the instructions that came with the wireless device for
more information.