There is a good article from microsoft on how to do this

http://support.microsoft.com/kb/842284

But sometimes the tools above don’t solve the problem. This can happen when the .ost file is corrupt beyond repairing.

What you can do in this situation is to look at the .ost file usually in the location %userprofile%Local SettingsApplication DataMicrosoftOutlook folder and rename the outlook.ost to outlookold.ost.
Start outlook again and let it create the .ost file again. It can take upto few hours. depends on the size of your inbox.