So there I was, I had completed a transaction at a 'save this page for your records' page that I wanted to a PDF. Ooops...I don't have Acrobat on this laptop. Luckily I knew I had the XPS 'printer' installed by default. (It comes with Vista.)
So I print it to an .xps file. it appears to 'print' successfully. The problem is, when I doublt-click it to open it, it opens in Firefox! Firefox is set as my default browser, but I find this weird - I thought there was an XPS viewer application. I right-click the .xps file and choose "Open With" and then "XPS Viewer". Again, it tries to open in Firefox. Firefox doesn't understand the .xps extension and offers to save the file for me, or let's me open it with "XPSViewer.Document (default)". Huh. Ok. I tell Firefox to open it with the "XPSViewer.Document (default)". Firefox opens yet another tab with the .xps document, offering again to save/open it for me.
I caught wind that you should try dropping the file into Internet Explorer. This works. IE recognizes the file and opens the XPS document for you. I also caught wind that this isn't just a Firefox problem, but rather a "default browser is not IE" problem. One solution to the problem is to re-associate the .xps file extension with IE instead of the "XPS Viewer" application. The other route (which I prefer) is to download the "XPS Essentials" pack from Microsoft. I think this pack was originally intended to add XPS functionality to XP and Server 2003, but it now supports Vista, and it appears to merge into Vista as some sort of update.
After I installed this update, double-clicking an .xps file still opened it in Firefox though! Come on! If I right-click on the .xps file, and choose "Open With", I now have a new item: "XPS Viewer EP". Ah-ha! This opens up the .xps file in it's own separate non-browser viewer. Perfect!
All that's left to do is make XPS Viewer EP the default app for .xps files. The first time I tried changing a file extension association in Vista, I went about it the way you do in XP - go to the Tools->Folder Options menu. But in Vista, the dialog that get for Folder Options doesn't have the familiar file associations tab that XP has. In Vista, you have to use the "Default Programs" Start menu item. (Just use the quick-search, or you should be able to find it under the Control Panel:
Just hit the ''Associate a file type or protocol with a program" item and you should be able to figure it out from there.