Yes, it is

In[1]:= $InstallationDirectory
Out[1]= "S:\\Program Files\\Wolfram Research\\Mathematica\\10.0.1"

In[2]:= $Version
Out[2]= "10.0 for Microsoft Windows (64-bit) (September 9, 2014)"

in the extremely unlikely case you used in your codes explicit drive names instead of invariant names like NotebookDirectory[], $InstallationDirectory, ... consult WolframSystemFileOrganization for all of them, you will find now a good opportunity to correct that.

You can install in on another drive, or just copy the Mathematica folder from

C:\Program Files\Wolfram Research\Mathematica

to D: or where ever. In the latter case, you will need to edit or delete and rebuild shortcuts (start menu, etc).

If you just move Mathematica, you should reset preference and cached files by holding down the SHIFT and CONTROL keys the next time you start Mathematica. (See http://support.wolfram.com/kb/12464 .)