I'm assuming by "D drive" you mean a partition on your main hard drive. If this is so, you can easily edit the partitions with an inexpensive partition editor; however, this will make all the data on the drive unreadable. Make sure to back up your data before messing around with partitions. I think some of the better partition programs allow partition changes without complete drive deletion, but I don't know as I have no use for partitions. And yes, you can make pretty much as many partitions as you want with any letter of the alphabet (except those associated with other drives, of course).