There's a semantic trap here:
Windows (and/or Windows USERS) often use "drive" and "partition" to mean the same thing. For example, if you create two partitions on one physical drive, Windows will see--eg-- a "C" drive and a "D" drive.
When you install Linux, the installer will see the drive and partition layout, and give you some options as to where to put things. If you have--eg--two IDE/PATA drives, you'll see hda and hdb---and for partitions: hda1, hda2....hdb1....etc.
You do not need to be disconnecting anything. The best way is to simply make sure that there is free space available---then let the installer help you set up the partitions. If you already have another NTFS partition created, that's fine---just convert it to ext3 as part of the Linux install process.