The most common causes include disk fragmentation, file system errors, outdated drivers, antivirus settings, and some other Windows features.
So what is the culprit that slows down the file copy? The confusion part is that nothing wrong with the computer, any other operation could be done just fine. Tons of Windows 10 users have reported the slow file transfer issue as above, either between two internal drives, an internal drive and an external drive, or between two PCs over network. I ran into a problem after upgrading to Windows 10, that whenever I try to copy files between two drives, the speed is extremely slow.
