Emails disappearing from inbox

Bewildered over this...running Vista and using Microsoft Office 2007, Outlook as my mail management program. Mail is disappearing from my inbox. it may stay for a quick visit but within seconds its gone. Or if i open another Outlook folder and go back to my inbox its gone in a flash. tried uninstaling and reinstalling Office twice now. my inbox folder is accumulating the mail as i see the counted mail number rising (ie Inbox(36) ). So its there but seems invisible and too shy to show its self. I have been prompted to use my 'inbox repair tool' but have no idea what its asking for when it asks me to type a file name to scan. How do i know which file to scan using this repair tool? Will using this really help the issue? Any help will be greatly appreciated! thank you