Disk C (main) is not include in the back up

My hard dive has 2 partitions C and G. The O.S is installed in drive C. When
I try
to do a Complete PC Backup when the Screen " Which disks do you want to
include in the backup?" appear it only shows drive G... so when the next
screen
" Confirm your backup settings " there is nothing in " The following disk
will be
backup:" So when I press "Start the backup" it shows message.
The backup failed.
The specified number of volumes is in valid. (0x80780010).
Note: My hard drive is partitioned after I install the Windows Vista
Ultimate O.S.
So What can I do to back up my computer ?