Each session of Microsoft Windows administration is like visiting Wonderland: even funny if not too often. The guys included a feature for shrinking/extension partitions starting with NT 6.0 (Vista), but the shrinking is of little use, except if used on a new installation, for they seem to have forgotten to supply any tool for consolidation of free space on a used partition.
What I figured out is the following procedure:
(1) Disable for the partition in question (1.1) system restore, (1.2) paging (swapping), (1.3) memory dumps, and (1.4) hibernation mode. These tend to create and maintain unmovable files.
(2) Apply Raxco PerfectDisk (the trialware version will do) to (2.1) "prep for shrink" and (2.2) "boot time defrag". I failed to identify any free utility with the equivalent features.
(3) Shrink the partition in question.
(4) Re-enable anything disabled on step (1) that you are going to need.