after a few days of tests. I'm almost 100% sure that JD2 can bluescreen the whole PC when checking checksum at the end of a download. this doesn't happen when I revert back to JD. not sure if this info helps, but I configure JD2/JD download all files to a sub-directory of a mapped drive. the mapped drive is a directory on another physical HDD, so the mapped drive itself is not a real partition.