It is possible, but I don't recommend it.
I personally prefer installing The Sims 3 outside of
C:, in a folder that gathers the files in one grouping. For example: the 'Base Game' goes into
E:\Games\The Sims 3\00-BaseGame, and all expansions are installed into their own directories beside that directory, e.g.,
E:\Games\The Sims 3\01-WA,
E:\Games\The Sims 3\02-HELS, and so on).
Do note that for The Sims 3, the majority of disk accesses are related to the loading of Game Objects, which are stored under
My Documents, which usually resides in
C:. So, by ensuring that the location of
My Documents is in
C:, you should gain significant speedup already.