Since Rockbox runs fine on the SanDisk Sansa C200 there are now C200 builds provided for download since a few minutes back. This being early C200 days, please have patience and don’t feel shy to step forward and help us smooth out the remaining quirks…
Sansapatcher is being remade to be able to install the bootloader on either e200 or c200 models, so until there’s an updated one available you’ll of course have a slightly harder time to actually install this on your c200.