As Flukester said, Windows is rubbish at moving large quantities of data so use an alternate method like xcopy, or my personal favourite Robocopy, which can be run as either a cmd line from a batch file or there is even a downloadable GUI version which makes life even easier.
It's a robust copy tool so even if files fail due to security errors or corruptions etc it'll continue with the next file and so on - and it can be set to log any failures to a txt file so you can check later how it's gone.