I've recently ramped up my Twitter activity and realized that there were a lot of programs out there to help you 'tweet' or 'twatter' :P.  Most of the apps are written with Adobe Air so you'll need that to run programs like Twhirl or Yahoo's Sideline.  So I installed Adobe Air and then proceeded to install Twhirl just to get the following error:

"Something went wrong trying to install this application.  Please install the latest version of Adobe AIR from http://www.adobe.com/go/getair and then try again."

But I already did! 

For some reason Adobe Air (in Vista) doesn't associate itself to .air programs.  Here's what you'll need to do:

_Find the .air file you need to install and Right click on it, Choose Open With > "Choose Default Program"
_Click Browse
_Paste this into the File Name:  "C:\Program Files\Common Files\Adobe AIR\Versions\1.0" - Press Enter
_You'll see "Adobe AIR Application Installer.exe", click on that and press "Open"
_Press OK

Now all of your .air files are associated to Adobe Air.