Well first you want to try and determine if you data is actually still available. Outlook 2007 stores the bulk of a users data in a file type called PST.
Here is detailed blog post with detailed information on it's location : here
Here is the short version:
- Open Control Pannel and select the
"Mail" Icon Select the Data Files
- Take Note the location of the PST
- Browse to this location and see if
you find any PST files
Ideally you want one that says Outlook.PST as this is most probably your active email. If you do not see an outlook.PST you may be correct in that your data may have been purged. If this is the case you will probably need to run some sort of data scanvenger / recovery utility such as R-Studio. If you see a file named archive.PST in the same location, this is most probably older email and not your active data. If you do find an Outlook.PST file you should be able to go into Outlook and select file and then open "Outlook Data File".
Caveat: Make sure you go into Windows Explorer, tools and options and check that you are showing all files and folders. The folder location that Outlook stores its PST files is hidden by default.
Im not sure what you can do to protect yourself from future registry key corruption other than be cautious. You can re-install Outlook but I would advise strongly in trying to determine if you data is still there prior to doing a re-install. If it has been purged you will want to run a data recovery program as soon as possible and cease using the computer until you do. Continued use will almost certaintly make data recovery a problem.