To keep your Documents in D: or E:
just copy your My Documents Folder to D:or E: then right click on My Documents(original folder - on desktop) and click on Properties and then change the target folder to the new location that is D: or E:\My Documents or ...

In this way all your documents will be saved in D: or E: Instead of saving on C:

Now just to make sure that it is done...save anything on My Documents and then goto D: or E:\My documents\ whatever you chose and check if the file is there. If it is there u r done.