If I install Unbuntu on the drive with Home on it in a seperate partition will I still have access to Pro on my D: drive?
Yes, if you do it right. You need to make sure you install Ubuntu in a separate partition. Linux has a different naming convention for drives and partitions. The drive will likely be referred to as "sda", the first partition sda1, the second partition sda2, etc...
You can use the partitioner that comes with Ubuntu, GParted to create partitions for Ubuntu. The first thing I would suggest before beginning is to defragment your windows partition. If you have the Ubuntu CD, put it in the drive and after it loads, look for a terminal/konsole and enter the command "sudo fdisk -l" to get partition information so that you will know how Ubuntu installer names your windows partition. This usually works pretty well and after a complete installation you will be able to boot Ubuntu and your windows partitions.
You can also modify your boot.ini file in windows to boot Ubuntu from xp.
Probably a good idea to post the results of the fdisk -l command to get more input.