Last month when Motorola announced the Droid Razr HD and the Droid Razr M, they highlighted the fact that some dated smartphones would not be receiving an update to Google’s most recent mobile operating system.

They did, however, promise to offer a $100 trade-in program for people using smartphones that can’t be updated to Android 4.1 Jelly Bean. Motorola is now making good on that promise as they have posted a list of phones eligible for the promotion. Don’t get excited too soon, however, as there is one small catch that you need to be aware of.

First, you must own one of the following handsets: Droid 3 by Motorola, Droid X2 by Motorola, Motorola Atrix 4G, Motorola Atrix 2, Motorola Admiral, Cliq 2 by Motorola, Motorola Milestone 3, Motorola Milestone X2, Motorola Electrify, Motorola Photon 3G, Motorola Xprt, Motorola Titanium or the Motorola Triumph.

If you have one of the phones mentioned above, you’re halfway there. Now here’s the catch – you’ll need to purchase one of the following new phones to quality for the $100 rebate: Motorola Atrix HD, Droid Razr M by Motorola, Droid Razr HD by Motorola, Droid Razr Maxx HD by Motorola, Motorola Electrify 2 or the Motorola Photon Q.

Alternately, if you own one of the following Motorola handsets, you’ll be able to update to Jelly Bean at some point in the near future: the Droid Razr M, Droid Razr HD, Droid Razr Maxx HD, Atrix HD, Photon Q, Electrify 2, Droid Razr, Droid Razr Maxx, Droid 4 and the Droid Bionic.

It’s worth pointing out that early termination fees will apply if you are still under contract with your existing handset. Under such circumstances, it’d probably be best to wait until your existing contract runs out instead of paying the ETF.