In some instances, your OS X disks may display all your applications as folders. When you double-click them, they open like folders to show the package contents, instead of launching. This usually happens after after a crash. There's a relatively simple fix, which you can see if you read the rest of this article.
The solution is courtesy of Apple's Tech Info Library (TIL), which you can find here:
http://til.info.apple.com
This site hosts all sorts of interesting material (I've added it to the links section); just change the drop down to "Operating Systems" and type (without the quotes) "OS and X" to find relevant articles.
The actual URL for this particular problem is: http://til.info.apple.com/techinfo.nsf/artnum/n106241
I've detailed the fix in the remainder of this article (modified from Apple's site).
You can resolve this issue when started up from Mac OS 9.x or Mac OS X. You must navigate to the filepath /Users/username/Library/Preferences and delete three files. Delete these three files in that directory:
LSApplications
LSClaimedTypes
LSSchemes
If you are using Mac OS X, logout and login again; if you're in OS 9, reboot into OS X. The correct icons should now appear.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20010328204820274