New to Outlook 2007 is the ability to search multiple PST files at one time. Any PST file (Archive Folders or Personal Folders) can be searched together with any others. This means that if you're searching for a message that you know you've filed away, but you're not certain which file you put it in, you'll be able to find it easily with a single search.
How? Make sure that the data files that you want to search are open (if they are, you'll see them in the Navigation Pane). Select All Mail Items as the location for your search and then select the files that you want to search. All Mail Items also appears at the top of the Instant Search pane so that you can clearly see that you're searching multiple files. We've shown an example in the picture, and you'll get a chance to try for yourself in the practice, which is coming up next.
Note If you have many PST files open, or if you have a few really large PST files open, it may take a while to search for messages.