What is the best default program to open zip files using vista?

Starting with Windows XP SP2 (might have been 3, but I really think it was 2), Windows Explorer has the ability to open up and compressed folder (ZIP files are compressed folders). Vista and 7 should be able to do this as well. Save the file to your computer (e.g., desktop, My Documents). After it downloads, right-click on the file, select Open With..., and the click Compressed (zipped) Folders. That should open it. If that works just fine for you, close the folder. Right-click on it again, select Open With..., then click Choose Program. Select Compressed (zipped) Folders and check the box that says to always use this program to open this kind of file. That will make it the default program. While WinZip is a great program, it's not exactly freeware, so after so many uses, you have to wait 20 seconds (or something close to that) each time it opens before you can do anything. The above mentioned method is free and comes built-in with Windows.

Winzip