Error -43 during conversion of audio file caf to aiff - windows XP

I received error - 43 during conversion of a caf audio file to aiff with Quick time Pro 7 on a win XP sp3 operating system .

I saved the file on a partitioned hard disk ( 120 GB ) , partition G .

It was not possible to carry out the conversion.

The conversion was only possible on a non partitioned external Hard Disk,

Is this quite regular ?