When your computer won't find the network:
Symptom:
Your computer is part of a Local Area Network, using
the TCP/IP protocol. It suddenly cannot find the network, or perform any network functions
such as shared Internet or printing to networked printers.
Cause:
This could be a number of things, including
malfunctioning network hardware. The most common cause, however is that your machine is
using the wrong IP address or Subnet Mask. An addressing conflict would cause the network
to disappear from your machine's point of view.
Solution:
Release all IP addresses and Re-boot:
Click Start
Click Run
Type winipcfg, and click OK. The IP
Configuration Utility will appear.
Click Release All
Click OK
Restart the computer