These tips may help you out.
Speed up the Start Menu
=======================
The default speed of the Start Menu is pretty slow, but you can fix that by editing a Registry Key. Fire up the Registry Editor and navigate to the following key:
HKEY_CURRENT_USER \ Control Panel \ Desktop \ MenuShowDelay
By default, the value is 400. Change this to a smaller value, such as 0, to speed it up.
Speed up the Start Menu (Part two)
==================================
If your confounded by the slow speed of the Start Menu, even after using the tip above, then you might try the following: Navigate to Display Properties then Appearance then Advanced and turn off the option titled Show menu shadow . You will get much better overall performance.
Andre