Technically, you can add a 120gb HD in your Xtra, but it acts sketchy on anything over 80gbs. I know several folks that have replaced the standard 30-40-60gb hard drives with 100gb and over and have horror stories of songs, albums and artists missing after they passed the so-called 16,000 track limit. A lot has to do with tags too ... making them short as possible, but the most tracks I have put on a hard drive is a lil more than 10K tracks. If you shorten the tags, it may not be as bad, but the firmware written by Creative stops at 16,000 tracks. And knowing Creative, they will never ever release firmware to support something that big. The only player that can handle it are the X-Clef family of players. So, the closest to it is an 80gb HD, seeming it's the closest to their 60gb one. Check out nomadness.net for all your Nomad needs ... I had 3 80gb units and all of the work flawlessly.