Disable the "ding" sound when initiating a call and ending a call.
hkey_current_user\controlpanel\soundcategories\incall
change the initvol to 0. do the same for hkey_current_user\controlpanel\soundcategories\incallfeedback
The sound is dpadctl.mid

Disable SMS message sent notification:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Inbox
3. Next, click on Inbox (make sure the Inbox is highlighted) and select Edit, New Key
4. Name the New Key as "Settings"
5. Click on "Settings" (make sure the Settings is highlighted) and select Edit, New String Value
6. On "Value name:", key in SMSNoSentMsg and in "Value data", key in 1

Credit for these: they were found on the TreoCentral forums -- usually from Hobbes