4
You can simply comment certain fields in register.php so they don't show. Two slashes "//" at the beginning of a line turns that line off.
You can also change the language constants used for other fields that you are showing so that, for instance, instead of the label for the textbox reading "ICQ" it could read "Department". In the database, the data would be labelled as ICQ, but on the View Account page, it would be ballened Department.
Good luck,
--Julian