View Full Version : Warning: Before Upgrading to Outlook 2007...

Alon Cohen
02-22-2007, 03:13 PM
If you are one of those people that always need to have the latest version of software, if half the software installed on your machine is in beta, or if you are just considering upgrading (or already upgraded) then this post is for you.

You may experience performance problems when you are working with items in a large .pst file or in a large .ost file in Outlook 2007. Short version is that if you have large PST or OST files, Outlook hangs, sometimes 10-12 seconds and may reduce your computer's speed. The cause is "To accommodate new features, Outlook 2007 introduced a new data structure for .pst and .ost files. In this new data structure, the frequency of writing data to the hard disk increases as the number of items in the .pst or .ost files increases."

More info at http://support.microsoft.com/?kbid=932086

Alon Cohen
03-29-2007, 05:51 AM
Update: we’ve experimented with this further – this problem only applies if you’re using Windows XP. This problem does not occur on Vista at all.

Alon Cohen
04-10-2007, 12:57 PM
Why does it happen to Windows XP?
I do not know why this happens, but there is a workaround that seems to help some people - full details can be read at http://www.microsoft.com/office/community/en-us/default.mspx?&query=outlook+2007+slow+on+XP&lang=en&cr=US&guid=&sloc=en-us&dg=microsoft.public.outlook.general&p=1&tid=44128537-a672-47d8-babb-d661c3790f4c&mid=44128537-a672-47d8-babb-d661c3790f4c

The short version (try this at your own risk) is:

Part of the issue comes from upgrading from Outlook 2003 or earlier because
Outlook 2007 uses your account settings to create new ones for you. When you
upgrade to 2007 you will need to locate four .DAT files and rename them...

STEP 1: Turn off Outlook 2007 and Locate these files

For some reason, during the upgrade these four files can become corrupted -
the migration from 2003 to 2007 isn't the smoothest but not having to create
all your POP3 accounts again is excellent.

1. extend.dat - you will find this file in the location | Drive
Lettter:\Documents and Settings\user-directory\Local Settings\Application
Data\Microsoft\Outlook\extend.dat //change it to extend.old

2. views.dat - may not find it most of the time

3. frmcache.dat - Drive Letter:\Documents and Settings\user-directory\Local
Settings\Application Data\Microsoft\FORMS\FRMCACHE.DAT //change it to

4. outcmd.dat - C:\Documents and Settings\user-directory\Application
Data\Microsoft\Outlook\outcmd.dat //change it to OUTCMD.old

STEP 2: Restart Outlook 2007

1. Send yourself some test emails and watch the messages appear.

We contacted Microsoft Office 2007 support and workshopped this fix with
them. They did not hear of this problem until we made first contact.
Together, with the help of their support team (merv m. specifically), we
found this simple solution above in a matter of 40 minutes. I was very
impressed with their willingness to work through a fix together.

As of today, they do not have plans to create a patch for this small bug but
they are gathering bug fixes for a future service pack down the road. Right
now (MS said) their focus is building a service pack for VISTA's bugs.

Good luck everyone!

Shane Keller
Keller Internet Marketing

Alon Cohen
04-16-2007, 10:02 AM
OK, Microsoft released an update for this on Friday. You can get the details at http://support.microsoft.com/?kbid=933493.

Note: I have not tried this on my computer.

04-14-2008, 04:30 AM
You can also get help from

06-23-2008, 07:10 AM
OK, Microsoft released an update for this on Friday. You can get the details at http://support.microsoft.com/?kbid=933493.

Note: I have not tried this on my computer.

07-28-2008, 04:08 PM
As an additional suggestion, please make all the office program use the 2003 compatible versions. The sales guys always want to use the latest and greatest version when they upgrade to Office 2007, but when their clients can't open their attachments because they were created with Office 2003 compatibility, you won't hear the end of it.

07-29-2008, 03:04 PM
Where is fine tool-ost conwertor (http://www.recoverytoolbox.com/ost_to_pst_convertor.html),
is a good way to recover data from *.ost format and convert it to files with *.pst extension,permit to convert *.ost file to *.pst extension, that can be easily read by any email client, compatible with Microsoft Outlook, read even corrupted files and you do not need to put any modifications to recovery process,made to recover your data from *.ost files,ost convertor to pst will never modify source files, so, if you are not satisfied with this program, you can always try to return back to the beginning of process.

02-28-2009, 06:29 AM
I read the post on the MS support site re: pst files - while it explains the problem, it doesn't seem to provide a solution? I guess it may just be a matter of stopping using PSTs as archives, but am hoping there is a better solution than that?

I have 10 PST files of 1-2 gig each that I have copied onto my new Vaio - though I have 4 gig RAM I am getting an error msg from Outlook saying it is out of memory/resources when I try to associate the files (I can get 5-6 of them in before it seems to run out of memory) - this is a real problem as I use the PST files as an archive/filing method, so I now don't have easy access to the files.

I am considering installing a 2003 version Outlook (as appears the issue w/ Outlook 2007 takes up too much memory ? ? ? so cannot handle many PST's?, which seems odd as I was using 2003 on a much lower spec machine and it handled accessing my PSTs then??) - but am hoping there may be a patch or solution of some sort that would allow me to use the software properly and not have to install 2003 as well to have access to my archives - appreciate any advise/suggestions.

11-26-2009, 11:10 AM
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11-26-2009, 11:26 PM
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11-27-2009, 05:09 AM
I close this old thread