I have my old generic PC (Widows XP Home) hooked up to a Linksys router (WAG325N). Another old Dell Optiplex GS280 (Windows XP Pro) connected with a Dlink DWL G122 (Rev C) UBS adapter. The Dlink adapter installed on the Optiplex no worries and I was off and running. However I now have a 3rd desktop (IBM Think Centre) running Windows Vista Ultimate. My first mistake was using the DLink install manual which was written for systems up to Windows XP. It didn't have the Vista drivers. After getting error message WZCSLDR.exe Entry Point Not Found, and then discovering I had to manually install Vista driverd from Dlink support I decided to delete my first attempt and started install again in correct sequence with the Vista drivers manually loaded in the Dlink folder. Eventually by highlighting the unrecognized hardware in Device Manager and clicking Update Drivers as per DLink support site directions, I got the system to successfully install the USB adapter on the Think Centre, SO then I went thru the 'connect to' procedure for Vista - again as per Dlink Support site directions. My Wireless router came up no worries and I clicked on it and typed in the password thinking I had the problem solved. However it will not connect. Its diagnosis says unknown problem. I have again consulted Dlink support site and done the obvious things as per their directions such as disabling the firewall prior to trying to connect. But still no success. Any ideas why the USB adapter can see my router but cannot connect?

Did you disable Windows Firewall to test it? Is it getting an IP address? Can you ping the router, domain names, or external IP addresses?

ipconfig /all to start. "Best Practices", Event viewer, host file, perfmon, are in my top 10