Well, today I managed to get into the serial port of the PMP. This is promising, since now I can load custom firmwares, and command the PMP to do stuff other than what iRiver intended.
If any of you want to repeat what I did, it would be wise to put a "voltage translator" in between your computer and the PMP, so you dont fry anything. The computer uses 12v for comm, the PMP uses 1.6 and 3.3v.
Make sure your comm program is set to 115200 baud. Then to access rrload, hold down "enter" before turning the PMP on. Now enjoy.
Here are some pictures as proof:
