I've been trying to manually back up about 200 Gb of music by transferring it -- drag and drop in Explorer -- from my hard drive to an external drive in Windows 7.
A few folders, no problem. Many folders... problem. I haven't nailed down a precise number, but it seems like every time I try to drag folders with over 10 Gb in contents total, Windows just... refuses. It doesn't do anything. No error messages, no nothin'. Just a complete lack of response.
If I try EXACTLY the same operation, but with only a few folders, it executes flawlessly. It's only when I'm trying to drag and drop a lot of stuff at once that it doesn't work.