Vista "Send To" Menu Hangs or Open Slowly

"The problem is almost always caused because Windows automatically puts items for each removable drive into the Send To menu, but could also be caused by having an excessive amount of unused items in the list. We'll cover how to get rid of both."

http://www.howtogeek.com/howto/windows-vista/why-does-my-windows-vista-explorer-send-to-menu-hang-or-open-slowly