If you're referring to personal folders that contain your files and
nothing else, this should be safe. However, if the folders are shared
so that remote users can see and/or edit the contents, the share will
be lost when you rename them. Additionaly, any applications that you've
explicitly told to look in those locations will be unable to do so
after you rename them.
As for application folders (C:\Program Files\Microsoft
Office\Office\Library, etc), if you rename then, some functionality of
the application will most likely be lost until you reset the names.
HTH
Jav