Outlook 2000 strange things going on

My boss the IT manager did it again, he walks over to my desk and says my outlooks broken. He was going through his email the night before and deleting old emails. He said his outlook looked funny but did not think about it. Ok more then half of his folders are gone he had about 45 or 50 now there are around 20. Any email he had in his inbox after the letter M is gone, people with the first name after M. I checked his pst file and it’s a little bigger then a gig. No error’s in the event viewer, we have exchange 5.5 on server 2000 and no errors there. He has never archived, nothing in the deleted folder. I went through all his settings in outlook, he seems to do these things quite offten. I guess thats why he is my boss:) Any ideas