I get stuck using windows MDI interfaces occasionally, the keyboard shortcuts that apply:

1. ALT+- (ALT+hyphen): Displays the Multiple Document Interface (MDI) child window's System menu (from the MDI child window's System menu, you can restore, move, resize, minimize, maximize, or close the child window)
2. CTRL+TAB: Switch to the next child window of a Multiple Document Interface (MDI) program
3. CTRL+F4: Closes the current Multiple Document Interface (MDI) window