Whaddya know what to do when you receive this error " Cannot start Microsoft Office Outlook. MAPI32.DLL is corrupt or the wrong version. This could have been caused by installing other messaging software. Please install Outlook. " after uninstalling Office 2007 and install Office 2003? Just a review, the correct Mapi32.dll file should be in c:\windows\system32\Mapi32.dll directory. If you search your computer and you see another Mapi32.dll file, simply rename it and reinstall your MS Office 2003 and it should correct this issue. Alternative solution: Go to C:\Program Files\Common Files\System\MSMAPI\1033 directory, rename the Mapi32.dll to Mapi32.old.dll file. Open command prompt Go to C:\windows\system32 directory. Run fixmapi.exe When you open Outlook for the first time, it will try to reinstall the missing file(s) and correct any issues from previous install. This should fix your Outlook issue. Please share your thought.