For my work I was also looking for this option and I tried this:
Log in as an Administrator and right-click* on C: then Properties and Security.
In Group or user names click on Users (for example).
The only thing I deny (check) is the Write option (Full Control and Modify will also be unchecked)
Then Apply and OK
Restart the computer
Now you will see that drag and drop (copy and paste) will not work in Windows Explorer (only in Documents and Settings\User) , but……
*by choosing C: the user will also not be able to save (for example a document) to C:, but only to My Documents, and installing programs is only possible if you are an Administrator
In the Advanced menu (Properties, Security, Advanced, Permission and double-click Users in Permission entries), there are more option to choose from. (or by choosing maps and secure them seperately, but that is a lot of work).
I haven´t tried the Advanced menu yet.
For me securing C: is enough
Good Luck
FrankL68 (from the Netherlands)