The way to get to user mode has been changed for version 2004 for windows. From the splash screen hold down the alt and shift key while right clicking. This will pop up a window that offers a variety of options. These are:

User Interrupt
Go to User Mode
(1) User/Custom Menus process
(2) Cache Manager
(3) $4D Compiler

This menu will also display additional processes that you may have created.

Choose "Go to User Mode" and you will be taken to the user mode.

Note: you can also use the Goto User mode action associated to a menu item or to a button in your form.