How fast or slow submenus appear when your mouse is over a menu, is dependent on the MenuShowDelay value. For faster fly-out menus, reduce the delay interval using the following Windows NT / Windows 2000 / Windows XP registry hack :

Hive: HKEY_CURRENT_USER
Key: Control Panel\Desktop
Name: MenuShowDelay
Type: REG_DWORD
Value: 400 ms default

Setting MenuShowDelay too low, can actually hurt performance if Windows is using too many cycles creating and destroying undesired menus. This is a personalpreference item. Experiment to see what value works best for you. I like a fairly low value with zippy flyout menus. I don't like to navigate menus under Start in geological time.