I've seen some forums (of other games) where all kinds of people were crying about a topic on how to make another drive.
It's actually very easy to change your drive numbers and to create another drive.
Lots of the current computers start with a C:/ drive and a D:/ drive where D:/ is used for recovery of the windows files (for example).
Let's say we have a 750gb pc. We have a C:/ drive and a D:/ drive.
We want to add an 'A' drive, for other files so they won't affect the very important back-up drive.
To get the A drive you'll have to do this:
Windows XP users: Go to menu Start and run 'run'. Typ in:
diskmgmt.msc and click run.
Windows 7/vista users: Go to menu start and typ in the search thingie: diskmgmt.msc and click run.
this screen will pop up:
As you can see I've already added an A drive.
Right click on your biggest drive where you have a lot of free space available, and click 'reduce volume' and let's say we put 50 gb (=50.000 MB).
In my case the C drive got reduced by 50 gb. These 50 gb will remain floating around till you assign a 'name' to the free space.
At the right bottom of the diskmanagement screen you'll see your 50gb of unassigned space. Right click it and click ~Change drive letter and paths.
Leave everything unchanged and change the letter to your likings.
Now your new drive should be ready to use, good luck with it