[X4U] Can't Write to USB Drive

[Neil]

I copied some of my friends home movies from VHS into iPod compatible mp4.  He brought me his portable USB hard drive from his Windows pc to me, but I got some kind of "can't write to this volume" error message when I tried to copy his videos to his drive.  I have no trouble reading the contents of his drive.  It has his iTunes music on it so he can take it with him to the bar where he DJs.  The drive had plenty of free space and I didn't use any kind of DRM on the video files.  Does anybody have any idea what is going on and what's the easiest way I can give him his videos?  I thought it would be easier to copy the files to his hard drive rather than burning a bunch of data DVDs.  Thanks.

Neil