The system & boot drive letters *might* change on reinstall (I've done this), but you will have no *easy* control over how the default lettering goes. Typically, primary partitions on each HD is lettered first over all of the hard drives (starting with IDE primary-master). Then, logical drives get lettered.
What I have noticed is that if you create a partition during the Win2K install, it's drive letter will be after the highest-lettered volume found during boot up. For instance, if I already have letters for C through H, but create a new volume on which to install Win2K, that new volume will get I: even if it lies physically between C and D on the HD. If I did a reinstall onto the same volume that I created during the first install, that volume would likely get D: this time and not I: again.
So, what is your best bet? Layout ALL of your partitions *before* beginning the Win2K install. Create bogus partitions if you want a higher driver letter for the system drive (boot drive will probably still be C:, no matter how hard you try

). Later go back and delete bogus partitions and the letters won't automatically change **in Win2K**. They will likely change in Win9x/ME.
-SUO