Sony PCG-Z505R - Manual (Page 79)

Using the System and Application Recovery CDs 69
Hard Drive Partition
In order to improve the performance of your computer’s DVgate™
Motion software, the hard disk drive on your computer has been
formatted with two partitions, C and D. DVgate Motion saves files to the
D partition. This prevents large video captures from consuming the
available space on your C partition. To maintain optimum performance of
DVgate Motion, you should defragment your D partition regularly. See
the DVgate Motion online help for more information.