The MPC 500, like all new Akai MPCs, uses the standard WAV file as its native sample format. Like it's larger siblings, it is limited to 16 bit rather than 24 bit as per the mpc 4000.
The program format for the MPC 500 is identical to the MPC 2500 and MPC 1000, so all programs are interchangeable and most parameters are transferred (the MPC 2500 has enhanced filtering, so these are not carried). One issue with using MPC 1000 or MPC2500 programs is that as the MPC 500 only has 48 pads per program, you'll 'lose' access the any samples assigned to those missing 12 pads.