Dimension and Fact for same entities?
I expect I would have a drive_usage fact table with a link to a snapshot time dimension, a drive dimension, a computer dimension and the various numerical facts about the drive at that instant in time.

There should probably be nothing regularly changing in the drive dimension - I guess it depends upon your definition of drive - is it a physical drive or a logical unit or what.  Perhaps your "C" drive has a serial number, and it's replaced - then the dimension will expire and a new dimension is added.  These things about a dimension are not really "facts", they are attributes.  This wouldn't affect reporting because the data for computer X, drive C has continuity.  Similarly if computer X is upgraded from dual core to quad core and so there is a change to the dimension (assuming something beyond number of cores is not tracked in a fact table, like a motherboard revision).  The capacity of a drive would be in the fact table, so changes to that over time are just new facts with new dates.  Sometimes you can even model changes to membership as facts.  i.e. if physical drives 1-5 are in logical drive C one day and then physical drives 1-6 are in logical drive C the next, that might just be a fact change in the physical drive membership fact table.  These are what some people call factless fact tables, since the only fact is the existence of the row shows membership - there is not much to be done except totalling or counting.

When you get into folders, modeling the hierarchy can be a lot more tricky depending upon what you are trying to achieve with rollups.

There is a lot of art to DW modeling in domains which aren't run-of-the-mill scenarios.