My Outlook Express address book became corrupt.  I was unable to open Outlook Express at all.  The address book was the same one I had in Outlook.  I copied the address book from Outlook and then reinstalled windows.  I put the same version of Outlook BACK on the computer.  I have tried to copy the address book back to Outlook but keep getting the ERROR message that the .pst file is incompatible.  What can I do?Did you obliterate all .pst files on your hard DRIVE, when you reinstalled Windows?  Are you sure you backed up the correct one?  What method are you using to open the .pst file?  What error message are you seeing EXACTLY?OK, I have tried to fix my problem but have now encountered a new one.  I went to another computer and typed in all my addresses.  I have most of them in groups.  I typed them into Outlook Express (version 6).  I tried copying the .wab file and then copying that file onto the new computer but when I open the address book on the new computer nothing is there.  I have tried looking on the internet but so far everything I see says that you cannot move a "group" from one computer to another.  Is this true?  If not then can you tell me how to do that?That just happened to me yesterday but it corrected it self. After about an hourCorrected itself??? Must have been the hour waiting.  corrected itself?  I don't understand, everything I read says you cannot move groups.  My question is, is this true?  As far as correcting itself, I don't understand what you mean.....after an hour you looked again and it was all there?    :-?