I installed Vista the other day only to find out the DHCP Broadcast was taken out of the default settings for the network interface.  As a result Vista couldn't find my Linksys router, to say the least I was annoyed.  I searched around and found the KB for the issue and wrote a quick little program to alter the registry.  (The reason I made it a program is I will be patching a bunch of machines and wanted an easy way to apply the patch.  And seeing as how the network interface guids are not the same from machine to machine I needed to use a sprinkle of logic).

You will need to run the patch as Administrator to allow access to the registry. After applying then reboot your machine and your network problems will have vanished.

You can always alter it maually or use this little timesaver:
VistaDHCPFix.zip (3.08 kb)  (Requires .NET 2) 

KB:
http://support.microsoft.com/kb/928233