Unopenable Outlook PST
File Recovery Freeware
I don't have too much experience with this, but running Scanpst.exe is painless (although it can take awhile). Also if you have Outlook 97-2002 and your PST File is over 2 GB in size, than your problem is easily solved with the crop tools though not without a small amount of E-mail loss.
PST File Corruption Recovery - this section features the PST repair tool which is installed by default with recent Windows versions.
Oversized PST File Recovery - with PST files from Outlook 2002 (XP) and before, they had an upper size limit of 2 GB. You'll get no warning and if your file gets bigger than this, it simply won't open. This section has a Web page and 2 tools which should allow you to recover from a such a situation. Outlook 2003 does not have this problem.
Text Extractors - if nothing else the text from a corrupt PST file can be extracted. You may be able to reconstruct your messages at that point.
Please note: Honestly the commercial software and services is the route you will sometimes have to take to recover your data. That's not to discount the large number of high quality data recovery freeware generously given away by developers that you can see here. On those occasions that you try the freeware and it doesn't work, the software in these pages will appear not be worth the time and effort you put in and this can be frustrating. I try to point out at the top of each page, what I see is the likelihood that and difficulty with which freeware can recover your data.
The Google Adsense Ads displayed on the pages should lead you to the standard commercial software and services available for the problem you are having. You can also try the commercial links by clicking on the Navigation Bar by that name on the left. It's also here.
For commercial software always be sure to try the demos first to see if the program works before buying. Also the difference in prices for software that does the same thing, for instance recovering PowerPoint Presentations, can be a large range like in this case $50 - 299. If possible, try several software solutions before buying. For services, be sure there is a no data, no fee guarantee, and a recovered file preview available.
I can also provide help but am limited ethically and financially (and legally in many cases) to using freeware too. I am perfectly within bounds to use most of the existing commercial office suites to recover corrupt office files since I paid for licenses for all of them. If you need help, I charge $22 for the first half hour and $22 for unlimited time after that. You can E-mail me at firstname.lastname@example.org.