Overriding HOMEDRIVE and HOMEPATH as a Windows 7 user

Problem

My employer has an Active Directory group policy which sets my Windows 7 laptop HOMEDRIVE to "M:" (a mapped network drive) and my HOMEPATH to "\". Since I have read-only permissions for the root of that shared drive, I cannot create files or directories in my windows home directory. My attempts to work with the IT department have been unsuccessful. Is there a way for me to globally change these envars at boot or login time? I need for all applications to use alternate values (such as "C:" and "\Users\myname"). I have some installed utilities (like gvim and others) that store preference files in the user's home directory. IMPORTANT: Changing these envars under "System Properties > Environment Variables" does not work. I have tried setting these as both User and System Variables (including a reboot). Typing in a DOS window clearly shows that my settings are ignored. Also, using "Start in" in a Windows shortcut will also not solve this, as I need things like Explorer context menu items (…