I'm replying to this old thread because I'm having a similar issue. Noticed my C drive was filling up and digging further found that nearly 8 GB was from MC 19 and MC 20. This seems especially odd to me because I installed MC, like all my programs, on the D drive. C is only for Windows. Why is JRiver collecting such a huge amount of files, and why is it doing anything at all to my C drive, I'd just prefer it remain where I put it and not bloat up my OS drive.