Bernoulli wrote on Aug 17^th, 2013 at 3:26am:

In fact, I want to load TrackIR-5 and AlacrityPC but both try to install on the C drive. Where should I install these? Thanks for any comments. :)

Why not create a Program Files folder (no need for a Program Files (x86) folder) on one of the other drives and install them there. Most software gives you the chance to choose where to install them.
My TrackIR software is install in C:\Program Files (x86)\NaturalPoint\TrackIR5, but my C: drive is a 300GB partition on a 1TB HDD, so it didn't matter that I installed there. ;)