I am using Windows Vista Home Premium on my Dell XPS M1330 and very often face wireless connectivity problem at my home. It works excellent at my office, but when I go home, recently I find connection with only Local access and no Internet connection.
One of the reason may be the signal is very week as the ADSL Router is in a different floor. I use a Wifi Antenna to boost the signals and it was working fine till last weak.
While Googling I could find that the Wifi connection with Vista is a common problem
Some of useful links are given below
Interesting Links
Windows Vista Update History - Windows Vista can be update automatically. In th Boosting wifi reception of your laptop - I just moved to a new place and for using internet



