I know this issue has already been raised by at least one forum member but here's my experience. I use 2 TB My Passport Ultra mobile USB 3.0 drives to store media content and also for backups. All my of external drives were just about full so I bought a new drive yesterday and started with the 'My Music' folder which contains all my music and iTunes media from the old drive to the new one. There is a lot of data on this drive - the My Music folder is as follows: 758 GB (814,719,983,675 bytes) 32,188 files. 11,976 folders When I do this copy on my old Dell laptop it gives me a meter showing how much data has been along with a percentage complete and a graph of how fast the data is being transferred, along with listing each file as it's copied. The throughput averages about 18 to 19 MBs per second. But I decided 'hey, I should be doing this on my new Surface Book,' so I moved the drives to the SB and started the copy. It starts off fine, some files are moved over but pretty soon nothing happens - it is stuck on one large file it thinks it's copying, the percentage complete never gets above 0% and the speed remains at 0. The copy is just stuck. I opened Device Manager to see if the USB port has lost the drive or drives as another user here has seen but it looks good - both external drives are still listed. It just doesn't copy. Could this possibly be a software problem that a future update might address? I use external drives extensively for work files, music and video media, etc. I cannot rely on a second computer to do copies and backups. If this is a hardware issue or limitation I'm going to have to take my Surface Book back, and I am really not looking forward to that.