As Vog says, the Pro version, about £38, will defragment multiple volumes. It will also do a boot time defragmentation which the Home Edition will not.
You should maybe have a look at PerfectDisk when comparing what you get for your money as you can get a 35% discount on this at the moment and it will do a boot time defrag. (To get the discount you need to go to the Diskeeper trade in section of the PerfectDisk site where you will be offered a 20% discount. You will then be sent an email offering a further 15% discount. The total cost ends up about £20).
DiskeeperLite is free but you probably already know.