In Total Commander you can configure the buffer sizes used while copying. Maybe in your homework you chose the right buffer size too (and, of course, asm is fast, but hard to write, I'm sure you didn't bother too much with error checking and other "small" problems).
Moreover, the optimal buffer size is different for small and large files, maybe Windows is not optimized for large size like a DVD image.
As for Total commander example, that was out of the box experience, without any tweaks. I just wanted to point out that even when using emulation layer to access Windows native filesystem type, Linux was significantly faster on file system operations.
As for my homework "copy" command, I know that it is not fully replacement to file copy windows command, but if copy operations takes >10min, all those checks and additional tasks shouldn't make IO bound operation take couple time longer than what some student implemented as homework.
Moreover, the optimal buffer size is different for small and large files, maybe Windows is not optimized for large size like a DVD image.