http://www.rogerlinndesign.com/support/faq.shtml

Q: How do I expand the MPC3000's (or MPC3000LE's) memory to 32 megabytes?

A: Despite Akai's claim that the maximum MPC3000 memory is 16 megabytes (using two 4 MB SIMMs and their proprietary 8 MB memory board), it is actually 32 megabytes, or 380 seconds of sample time. Their stated reason for claiming a maximum capacity of 16 MB is that the MPC3000's disk system has a limit of 30 MB per disk partition, which prevents you from saving a full 32 MB of sample memory to disk. We think you'd prefer to have the choice. To expand an MPC3000 to 32 megabytes:Buy two 16 megabyte, 30 pin (not 72 pin) SIMM memory modules. Any speed will do, parity or non-parity.
Disconnect the power cord and open your MPC3000 by removing 4 screws at top of rear panel, 4 screws at left edge of bottom and 3 screws at right edge of bottom, then lift up the front end of the front panel.
In the two SIMM sockets located in the center of the bottom of the unit near the front edge, install the two 16 megabyte SIMMs.Push them into the sockets until they snap into place. If they don't snap, you may have put them in backwards.
Look for the small, 2.5 inch square board in the front right corner of the bottom of the unit. This is Akai's proprietary memory board, containing either 2 MB or 8 MB. This is no longer necessary so remove it. (If you leave it in, it will simply duplicate a portion of the 32 MB provided by the 2 SIMMs, and therefore won't increase memory past 32 MB.)
Do not ask us any questions about this. This is all the information you need and there is nothing more we can tell you.