Repair corrupt Outlook PST files with two Microsoft utilities

by Brien M. Posey MCSE | Jun 13, 2002 7:00:00 AM

Takeaway: Outlook PST file corruption is a fairly common occurrence. To help you troubleshoot PST failures, Microsoft provides two handy utilities: the Inbox Repair Tool and the Oversized OST And PST Crop Utility.

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For those who support Outlook, PST file corruption can be an all-too-frequent occurrence. Such was the case for TechRepublic member Jpelillo, who suffered such a corruption when upgrading from Windows NT to Windows 2000. "Why do Outlook PST files corrupt when switching from NT 4.0 to 2000 on workstations, and is there a patch to fix this problem?" Jpelillo asks in our Technical Q&A.

While I’ve personally never encountered the corruption issue while trying to upgrade, I’ve seen plenty of other cases of PST file corruption. When this happens, the Inbox Repair Tool and the Oversized PST And OST Crop Utility can help. Here's how.

Always make a backup
To address Jpelillo's specific migration issue, I would recommend the same technique as given by TechRepublic member Florinel who wrote, "Try in WinNT to export to a file and then import in Win2000." Your PST files could become corrupted after an upgrade, so back up the files prior to upgrading. Another option is to rename the PST files to something other than Filename.pst, and then rename them back to their original names after the upgrade.

Of course, this solution only prevents future corruption; it doesn’t correct the corruption that’s already occurred. There are other solutions for this problem.

Using the Inbox Repair Tool
To fix corrupted PST files, you can use the Inbox Repair Tool. However, the tool isn’t always able to repair every PST file. It works by repairing the PST file’s header and then deleting anything in the file that it doesn’t understand. So if a PST file’s header is damaged, as may be the case for corruption that occurs during a version upgrade, the tool should have no trouble making the repair. But if the data within the file is corrupt, the Inbox Repair Tool will likely destroy what’s left of the file. That's why it's always good to make a backup of the PST file before running the Inbox Repair Tool.

The Inbox Repair Tool is located in the C:\Program Files\Common Files\System\Mapi\1033\NT directory of any system that’s running Windows 2000 or Windows XP. The tool’s filename is Scanpst.exe. Other versions of Windows also include the Inbox Repair Tool, but the tool’s location varies among these earlier versions.

Using the Oversized PST And OST Crop Utility
Another possible cause of corruption is that a PST file has a 2-GB size limit. Once this limit is exceeded, corruption occurs instantly. You can’t initially fix this problem with the Inbox Repair Tool. Instead, you’ll have to use the Oversized PST And OST Crop Utility first, and then follow up with the Inbox Repair Tool. The crop utility works by deleting about 25 MB of data from the file to bring the file back within specs. Use this tool as a last resort, because you can't control what data you lose when using it.

Because of its destructive nature, the tool is unavailable for download. You can only acquire the tool by calling Microsoft’s Product Support Service line at 800-936-4900. Microsoft charges about $200 for calls to this number, and when you call, an operator will ask you for a credit card number. According to numerous sources, if you explain to the operator that you just need a copy of the Oversized PST And OST Crop Utility, but don't need help using the tool, you can get the tool without being billed. You can get more detailed information from Microsoft by reading these Knowledge Base articles: Q197315 and Q296088.

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