Outlook PST files are physically 'shrinking' before my eyes..and cannot be read

We've seen this on 3 machines here.. Outlook 2k pst files appear to have no information in them anymore.  The size on disk will be 40MB,100MB, etc. Within outlook when you check the folder size, the only folder that will show under the pst file will be deleted items and the file size (w/in outlook) will read as 0 bytes.  If you open explorer and look at the file you will see it start to shrink.  A few kb every couple seconds.  The only way to stop the shrinking is to close outlook.  

We've explored the idea of a virus - not likely, they are all running up to date sig files.  At this point, I have absolutely no idea.

I almost forgot, we've of course run scanpst.exe and the machines are not fragmented either.  They run diskeeper every night.
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slink9Connect With a Mentor Commented:
It definitely sounds like a virus.  Try http://housecall.antivirus.com
It is free and always updated.  It could be a brand new virus that the virus software has not yet conquered.
AlginaldConnect With a Mentor Commented:
Is the .PST the only messaging system implemented?

If you're also running against an Exchange Server, and the default delivery location is the Exchange Server, the the e-mails will sometimes be re-homed to there automatically.

Try creating a new profile, with only the .PST file in, and then see if it shrinks.

anheuserConnect With a Mentor Commented:
The users may be deleting the mail from their Personal folders.
Hear me out.
If your users are deleting mail from their PST files the file size when vied within outlook will get smaller, but when you browse to the PST file from within Windows and check the size by looking at the file properties the file size won't have changed.  

The mail is removed from the personal folder and the size drops whne you check it in outlook but the ACTUAL file size does not drop.

This happens sometimes and is an error in Outlook.

To fix it see Microsoft Knowledge Base Article - 245776


Here is an easier solution to get the actual PST file size in sync with what Outlook says it should be:
1. Export the original PST file as a PST file. Name the NEW PST file  something different.
2. Remove the original PST file from the user's outlook profile
3. Add the NEW PST  file to the user's profile
4. Once you make sure everything went as planned you can delete the original PST file.

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