When using a USB external hard drive on my old computer with Windows XP, I could delete and add videos with no problems, and then simply defragment that drive from time to time. Now with my new computer and Windows 7, I am finding that when using the same USB external hard drive to delete and add videos, I am having problems. I remove unwanted files by "moving" them to a folder on my new computer and then when I attempt to copy a new video from my computer, it won't transfer even though there is plenty of storage space on the USB external hard drive. I have found that if I run the error-checking program on that external hard drive, then I am able to transfer files, but that seems very time consuming. Anyone have a solution as to why the external hard drive is acting like it is full when actually there is plenty of space??? The external drive is formatted as NTFS.