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Outlook cannot open .pst file which was in use by an unknown program

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We have a small "workgroup" network - 3 users, 3 computers running XP and MS Office 2003, 1 Buffalo TeraStation NAS, no servers


On each PC, there is a U: drive mapped to the user's personal folder on NAS


One of the users intermittently got an error when opening his Outlook

"Unable to open your default e-mail folders. The file U:\Mail\Outlook.pst is in use and could not be accessed. Close any application that is using this file, and then try again"


The problem happened on Sep 20 for the first time. I restarted NAS, restarted the computer, no joy. I killed the tasks of MS Security Essentials and Google Desktop, etc, that seemed to fix the problem. So I told the user to leave Outlook open, do not close it.

I checked this computer yesterday, Outlook worked fine. I ran scanpst.exe against the pst file on NAS, I opened and closed Outlook a few times, the problem did not show up at all.


Today, the user called me because the problem came back again.

I spent an hour but could not fix it regardless what i did. I even disabled all third party services and programs from MSCONFIG, but still no joy.


I installed "unlocker" but it said that nothing was opening the pst file, while there must be something!


The other 2 computers are totally fine.


I am wondering if you know any program like "unlocker" that is able to detect which program is using the .pst file.

Or if you have seen this problem and know the solution?



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Natalie Green

Natalie Green


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Visit this link to know what is wrong with your file.

If it still doesn't solve your issue report back.

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This problem might be occur due to corruption in MS Outlook Data File.You can try Inbox Repair Tool (Scanpst.exe) to diagnose and repair errors in the corrupted PST File.


For more information about this issue,click here: http://www.article.m...0x80040116.html



Thanks & Regards

Paul Hogan

Edited by paulhogan, 17 July 2015 - 12:01 AM.

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