So it took a lot of fiddling, but I finally found a way to install Rockbox via getting a newer bin file from Sandisk. Had to update their firmware before putting that bin file into the utility, and once I did that, the install was no problem.
However....Now it's been about 15 minutes since I got the "Install successful" message, and I can't eject the player from my computer. I've tried the tray eject window, the "eject" button in the Utility, and the device manager, and they all say that files are in use and it can't be removed. Should it take that long to finish transferring? I can see on the player that rockbox is there...but what could the problem be? I'm nervous to just take it out.
Help!