sounds like a good time to reinstall outlook!
do a search for files called *.pst and *.wab first and copy them to another location. Then remove outlook (or office) from add remove programs in control panel and then reinstall
You will have to enter your email account details again, so you'll need your incoming and outgoing server names, login name and password.
Then if you copy the two files you found earlier (outlook.pst and outlook.wab) back to the original place you found them this will restore all your mails and address book