A Repair Install is a good idea, but should be left as a last resort. Go to Start/Run and type control userpasswords and press enter, open your user account make sure you are a User with Admin rights and not a limited user. Limited Users cannot access certain areas like Internet Connections. If you are an Admin, then create a new user account with admin rights. Log out of the user profile you are in and log in as the new user. Try going to Internet Options now. If that doesn't work, then log back into your old user profile and if you have an XP CD put that in the drive, and go to Start/Run and type SFC /scannow and press enter. It will replace any missing system files from the CD.
If the new profile does work, while logged in as the new user, browse to C:\Documents and Setting open up your old user profile, Copy Desktop, Favorites, My Documents, and Start Menu files and Paste them into your new user profile folder overwriting the empty ones and always use this profile.