Did you use jupgrade?
If not the process is quite complex. Your new site will show only the fields that have been installed or cb. To move cb, the best approach is have the same version of cb on both 1.5 and 1.7. Do a Jupgrade and just copy the relevant tables. CBJUICE is most useful only for moving data if values have changed or new users have come in to your 1.5 site after the migration.
Note, you can transfer your old fields, plugins etc only by careful copying of the cbtables and appropriate folders from one site to another. If you are not totally familiar with CB, I would advise getting some help or creating a clean site and then moving the users with cbjuice. NOTE, CBJUICE does NOT support cbsubs. You will have to do the table moves for that.
Note, you can only move the user tables and cb tables from a site that has been processed with jupgrade because you need something to create the 1.7 ACLs (WHICH ALSO MUST BE MOVED).