The hell to exprimental copy files in W8 to NAS

I'm testing with router is best to copy my movies to and from the NAS. But Windows 8 still copy's files after I brake the operation. It seems want to b finnish anyway (the procces is bussy with another program). If you delete the big files its waiting tills the file is finish to the disk. No reboot of windows and the Nas help. I now have the slowest network in the universe. I think I have som terabyte flouting around now.

Help pleas!