Usually this happens when you have iether a newer version of Microsoft Office and then you install an older one, you may see this error when opening Outlook.

Cannot start Microsoft Office Outlook. MAPI32.DLL is corrupt or the wrong version. This could have been caused by installing other messaging software. Please reinstall Outlook.

To fix this, do the following:

Open C:\Program Files\Common Files\System\Msmapi\1033
Delete MAPI32.DLL
Rename MSMAPI32.DLL to MAPI32.DLL
Start Outlook