I have been stuck with this problem for months. There are 2 .inProgress files currently in my trash on my external hard drive that I used for back-ups with Time Machine. I stupidly deleted them when I received an error message about Time Machine being unable to complete a back-up and I instantly regretted my decision! I have tried the sudo rm -rf command lines with the files with no luck. Here is the garble I receive from terminal when I attempt to delete either file: danas-imac:~ dana$ sudo rm -rf /Volumes/Dana\'s\ back-up/.Trashes/501/2014-09-09-235304.inProgress Password: rm: /Volumes/Dana's back-up/.Trashes/501/2014-09-09-235304.inProgress/.Backup.432013984.876549.log: Invalid argument rm: /Volumes/Dana's back-up/.Trashes/501/2014-09-09-235304.inProgress/B855BBA7-18F4-406C-8B00-BB5FAD053BCF/.exclusions.plist: Invalid argument rm: /Volumes/Dana's back-up/.Trashes/501/2014-09-09-235304.inProgress/B855BBA7-18F4-406C-8B00-BB5FAD053BCF: Directory not empty rm: /Volumes/Dana's back-up/.Trashes/501/2014-09-09-235304.inProgress: Directory not empty I'm wondering if anyone can help with this! I can't erase the external drive, as the files are "in use" and the drive therefore, can't be unmounted. I can't reformat the drive for the same reason. I can't even eject the drive from the desktop, as the computer states the files are in use. Time Machine is off during all these attempts. I'm running an early 2009 iMac with Yosemite version 10.10.4.