M-Audio KeyRig 49 Features:

49-note synth-action keyboard
Includes keyrig software for PC
Assignable modulation wheel and volume slider
Pitch bend wheel
Assignable octave +/- buttons
Edit mode button
Sustain pedal input
USB 2.0 and USB 1.1 compatible
Instant installation on Mac OS X and Windows XP computers - just plug and play
Includes Ableton Live Lite (PC/Mac) software > make music right away
M-Audio Key Rig software (PC only):
Four top-quality virtual sound modules: SP-1 Stage Piano, MS-2 Polyphonic Synthesizer, MB-3 Tone Wheel Organ and GM-4 General MIDI
Use stand-alone or with a sequencer
Variable velocity and controller settings
Split and layer modules for performance combinations
Module and master effects processors
Compatible with most popular software
Ableton Live Lite music creation software

M-Audio KeyRig 49 Specifications:

Compatibility:
MME
Mac OS X Core MIDI

KeyRig 49 keyboard:
Pentium 3 800MHz or higher
(CPU may be higher for laptops)
256 MB RAM
DirectX 9.0b or higher
Windows XP (SP1) or higher
(Windows 98, Me, NT, or 2000 not supported)
*M-Audio suggests you also check the minimum system requirements for your software, as they may be greater than the above.

Key Rig software:
Pentium III 500 MHz or AMD7 (P4 / Athlon 1 GHz or faster recommended)
256 MB RAM
600 MB free hard disk space
Windows XP*
VST 2.0 compatible host software
CD-ROM drive for installation
Internet connection (on any computer) for software activation
ASIO-compatible soundcard for standalone operation
* Home and Professional Edition only. Windows Media Center Edition is not currently supported.

KeyRig 49 keyboard:
Macintosh G3** 800/G4** 733MHz or higher
(CPU may be higher for laptops)
OS X 10.2.8 w/ 256 MB RAM,
OS X 10.3.4 or greater w/ 512 MB RAM
*M-Audio suggests you also check the minimum system requirements for your software, as they may be greater than the above.
**native USB port required; G3/G4 accelerator cards not supported