A Digidesign Pro Tools LE hardware interface is the hardware audio interface, like your Mbox, that is supported with Pro Tools LE software. The list of supported interfaces with Pro Tools LE 7.3 can be found on this page:
Pro Tools LE 7.3 for Mac OS X System Requirements
http://www.digidesign.com/index.cfm?...4&itemid=24400
Pro Tools LE 7.3 for Mac OS X has the following system requirements:
Pro Tools LE Audio Interface Required
Pro Tools LE 7.3 supports the following Digidesign products:
003 Factory
003 Rack
Digi 002
Digi 002 Rack
Mbox 2 Pro
Mbox 2
Mbox 2 Mini
Mbox
FWx Record/Playback Option for VENUE D-Show Systems
...and additional system requirements on that page. Pro Tools systems are integrated software/hardware systems. The Pro Tools software will not work if the Pro Tools audio interface is not connected to your computer.
For more compatibility information specific to your Mac, see the main Pro Tools LE 7.3 for Mac compatibility page:
http://www.digidesign.com/index.cfm?navid=54&eid=3107
Click on the Compatibility link at the top of the DUC for the Pro Tools LE for Mac OS X Compatibility Grid, with update and upgrade information.