Ran chromeinstaller.exe and added googlecast app to Chrome browser
Chromeinstaller says: "No big deal, but your wifi is turned off".
Google cast says: "No Cast devices found".
System: Windows 7 (on desktop). Router: AT&T 2Wire 3800HGV-B
I have two other wireless dongles on my TV that my router does see.
Just for giggles I plugged in the Chromecast dongle right next to my wireless router to make sure it wasn't a distance problem; no joy.