More for you to try:
Have you done a System Restore
? Restore it to a point where it was working. If it didn't work move to the next one.
Click on Start=> All Programs => Accessories and right click on Command Prompt, select "Run as Administrator" to open a command prompt. Press enter after each command then if prompt to restart the computer, please restart.
Reset IPv4 TCP/IP stack to installation defaults. netsh int ipv4 reset reset.log
Reset IPv6 TCP/IP stack to installation defaults. netsh int ipv6 reset reset.log
Reset WINSOCK entries to installation defaults: netsh winsock reset catalog
Restart the computer after.
From the troublesome computer verify that all your network services are Started from Control Panel=> switch to Classic View then Admin Tools=> Services:
• COM+ Event System (for WZC issues)
• Computer Browser
• DHCP Client
• DNS Client
• Network Connections
• Network Location Awareness
• Remote Procedure Call (RPC)
• TCP/IP Netbios helper
• Wireless Zero Configuration ( XP wireless configurations only)
• WLAN AutoConfig ( Vista wireless configurations only)