Create a file /etc/fstab with the following contents.
# Identifier mount point fs type options1
UUID=3CA41C88-3E86-3A39-88CE-9379FF44B6A5 none hfs rw,noauto
The alphabet soup after the = sign can be found with diskutility.
(Fire up DiskUtility, select the disk, right click, More Information Universal ID)
FS tab needs the following ownership and permissions:
bash-3.2# ls -l /etc/fstab
-rw-r--r-- 1 root wheel 71 29 Aug 2011 /etc/fstab
To create the file try this:
sudo nano /etc/fstab
The noauto option causes it to not mount at boot.
In a terminal window type man fstab for other options
Not directly applicable to your problem: VirtualBox, VMware, and Parallels can run windows in a virtual machine. VirtualBox allows using a dedicated disk. (Others may, don't know) For applications that are not CPU or graphics intensive, or access the hardware directly this is often good enough. I run MS Access this way. Anything that needs DirectX may have issues or have an unacceptably slow frame rate. Action games don't work well.