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"Not responding" is a common message delivered from Windows when it is not able to communicate quickly enough with a program running on your computer.

Dear Leo, I have a BIG problem with Microsoft Outlook 2010. My operating system is Windows 7. Outlook keeps giving me the error message "Not responding," freezes, and then unfreezes or just hangs. I double-click and it will eventually unfreeze itself. When I highlight and want to move email to a folder, it says it cannot do this. But when I click again for the second time, it moves the email. I've had no luck in trying to contact Microsoft so I was wondering if you could help. I took my computer back to the factory settings and did a clean install of Windows 7 and Microsoft Office 2010, but that hasn't fixed things. Hope you can help.

In this excerpt from Answercast #39, I look at some common reasons why the message "Not responding" could be delivered by Windows.

Not responding

Well to be honest, I'm not sure that I can help, but I definitely have a few ideas about the kind of things that might be going on in this case.

What "Not Responding" usually means in Outlook is that it is just too darned busy working at whatever it is you've asked it to do, to actually respond to your mouse click or keystroke.

  • In other words, maybe you're downloading email and it doesn't have time to pay attention to what you're asking it to do.

Normally, that shouldn't happen. Outlook is architected to be able to respond to your user input in a timely manner without throwing out this "Not Responding" message...

  • Which is a Windows message, by the way; it's not an Outlook message.

Windows and Outlook

  • Windows is actually trying to communicate with Outlook, the program;

  • And Outlook is too busy working on something in order to respond – even to Windows.

Windows is trying to give your mouse-click or your keystroke to Outlook, and Outlook is just too busy.

Where's the hang up?

Now, what's it too busy doing? That's where things get kind of odd and interesting.

When I've seen this happen; when I have this scenario that you outlined:

  • It's usually something to do with the disk or the PST file.

The PST file itself may be too big. Sometimes, it's just spending so much time trying to manage the contents of the PST file that it is not able to respond to things (like your mouse clicks or your keystrokes) in a timely fashion.

Again, normally, that shouldn't be the case, but I could certainly see it.

Large PST files

I have, in fact, seen it on particularly large PST files; on PST files that are internally (I'll say) fragmented, because the same concept of disk fragmentation kind of applies to the contents of PST files.

Bad disk sector

In fact, the disk itself could be at fault. Certainly, things like a bad sector (or a sector on the disk that is going bad) can cause these kinds of issues in Outlook... or for that matter, in any kind of program that's writing to the disk.

So, another scenario to look at is:

  • Is there a sector on this disk that's going bad?

Give ChkDsk a run. Maybe consider SpinRite if that's an issue.

Software issues

Since you did a clean install, I'm actually not that concerned about things like additional software on your machine getting in the way.

The only other thing that falls into that category, however, are any add-ons that you happen to regularly use with Outlook. Outlook does have a fairly robust plug-in model. Particularly if you're in a corporate environment, there can be plug-ins.

  • Plug-ins can cause this kind of behavior as well;

  • Not intentional, but sometimes, they're just not written to handle all of the worst cases.

Watch your disk light

What I would recommend you do to try and get a sense for where this problem might be coming from is (of all things): pay attention to your disk activity light when you're having this "Not Responding" scenario.

That will tell you fairly quickly if this a disk-based issue.

So, what I recommend you do is:

  • Let your machine basically calm down after you boot it.

  • Let it come to a calm or a quiet state where it's done all of its scan;

  • It's done of all its boot-up work;

  • It's done whatever it's done;

  • Outlook is running, but the disk light is not really active;

  • The disk light is pretty much off all the time.

  • It will blink occasionally, but that's fine.

Now, start using Outlook. If your disk light starts going crazy; if it actually is on almost all the time, and at the same time, you start experiencing the "Not Responding" message that you've described in your question, then I strongly suggest that what you're experiencing is a disk-related issue.

  • That could be the disk itself;

  • It could be a problem with the PST file;

  • It could be a problem with Outlook's ability to write to the PST in a timely fashion.

Those are the things I would look at. I'm sorry I don't have something really specific that I can just say, "This is the answer for you." It's a symptom that can be caused by many, many different things.

  • The disk is the thing that I look at first.

  • The PST is the thing ON the disk that I then look at first.

Article C5636 - July 29, 2012 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

Reverend Jim
July 31, 2012 9:47 AM

One of the problems could be that your timeout value in Outlook is set too low. I find (especially at the cottage over a slower connection) that I need to specify a longer timeout, particularly if I have to send or receive large messages. In Windows 7 you can get to this setting via

Control Panel
E-mail Accounts
Select view or change existing email accounts
Click Next
Click Change
More Settings

set Server Timeouts to "long" (10 minutes)

and see if that helps.

July 31, 2012 10:53 AM

Did you install MS Office 2010 as 64 or 32 bit?
Microsoft has stated that even if you are running Win7 as x64 you should only install Office as x32 bit to prevent difficulties in running the software.
I found out the hard way that this is good advise.

July 31, 2012 11:14 AM

I agree totally with Lee -- make sure and install Office using the 32-bit install. That solved several problems for me. Plus, if you ever use any 3rd-party add-ons to sync with Outlook (like a phone app), chances are good there's not a 64-bit version.

August 1, 2012 2:24 AM

i had a similar issue that i was able to resolve, just like Leo has highlighted, it was actually one of the plug-in on MS outlook, precisely my antivirus, after disabling it, MS outlook was back to normal.

Tony Kightley
August 1, 2012 8:54 AM

I hesitate to recommend Outlook Express as it is supposed to be redundant! However, such problems as have been described are, often, cured by Ccleaner. I find it very useful in such cases.

Outlook Express is not redundant, it's outdated and should be avoided: Why Outlook Express Must Die

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