Why can't I import and export moving images between the external hard disk drive of another manufacturer and my DV equipment with DVgate motion?

Why can't I import and export moving images between the external hard disk drive of another manufacturer and my DV equipment with DVgate motion?
or
Why can't I capture moving images or export files between the additional external hard disk drive of another manufacturer and my DV equipment?
* When I use the hard disk drive built in my VAIO computer at the factory shipped state, I can operate those functions normally.

Sony does not guarantee the normal operation of VAIO computers when a hard disk drive of another manufacturer is added.
To deal with moving images and other large files, the hard disk drive must be "stable and fast".
If you export them to a hard disk drive that is slower in the data transfer rate than what is installed to the VAIO computer at the factory shipped state, problems may occur in some cases. (If you use a hard disk drive connected to the machine through SCSI or a PC card)