Profile for new member vs renewal

[groston]

For our organization, the only information about Individual contacts we care to track is first name, last name, email address, company name, and city; with the first three being required and the last two optional. I have created a CiviCRM profile with these five fields and have associated this profile with the membership form.

Here's what's bugging me: If someone who a) is a member and b) is not logged into Drupal visits the membership page to renew, they are forced to reenter their first and last names. They should not have to do this - it seems that there should be a way to set this up such that the first screen only requires the email address, and if there is no Individual Contact with that email address, then the other four fields are shown.

Would you please offer some suggestions for accomplishing this?

Thank you.

[groston]

Thank to Mike Monan for providing this answer: Why not just ask them to login (protect that page) if they are trying to renew?  Have a link to a sign up page and from there allow them to click through to renew (where they will get prompted with the login box), and then everything should be filled in, no?

This is the approach I used, which led to one other technical matter, see https://drupal.org/node/2254391. Once resolved, the site will be ready for visitors.