Prevent Account Changes in Outlook Express

Start/Run/Regedit

“HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Outlook Express”
Value Name: No Modify Accts, Data Type: REG_DWORD (DWORD Value), Value Data: (1 = enable restriction). Create new DWORD value called "No Modify Accts" and set it to "1" to enable the restriction or "0" to allow users to modify accounts.

Restart Outlook Express for the change to take effect.