You might be able to accomplish what you want by adjusting security permissions for the C: drive (Right-click C: > Properties > Security > Advanced). Click "Change Permissions" > Add... and add the user account. From there you can set permissions for that particular user (i.e. if they can create new Files/Folders, etc...). That said, I've never done anything like this in practice. So please, please test this out first and make sure it'll do what you want without interfering with the OS.
The above is a little extreme IMO, so as another suggestion, you could encourage saving things to the E: drive by moving the default user folders (i.e. Desktop, Documents, Music, Pictures, etc... that show up on the left side in Windows Explorer). Just go to C:\Users\**User Name**. Right-click on the user folder you want to move, click Properties, go to the "Location" tab. From there you can move these folders to the E: drive somewhere. I'd for sure move the Desktop and Downloads folders since this is where most people seem to save stuff (and most browsers default to saving to the "Downloads" folder anyway). Moving Documents, Music, Pictures, and Videos might be beneficial as well if they save to these locations. Of course this doesn't prevent saving to the C: drive, but it might help since most people I know habitually use the default user folders since they are just there.
Edited by francisw19 - 1/10/14 at 2:41pm