try installing the following applications. Once you install the .cab files you should be able to make just about any tweak using one of these 3 programs
Diamond Tweak
Advanced Config
PHM Registry Editor - (anything that looks like this "[HKEY_LOCAL_MACHINE\Software\Microsoft\Inbox\Settin gs] Set SMSNoSentMsg to 1")
A big list of tweaks can be found here:
http://forum.ppcgeeks.com/showthread.php?t=42730
Good luck!!