It is possible to control the interval used to delay the appearance of the cascading menus when you click Start on the Taskbar.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
To change the Start menu display interval, follow these steps:

1.	Click Start, click Run, type regedt32, and then click OK.
2.	On the Windows menu, click HKEY_CURRENT_USER on Local Machine.
3.	Click the \Control Panel\Desktop folder.
4.	Double-click the MenuShowDelay value, type a number representing the menu display delay (in number of milliseconds) in the String box, and then click OK. You can enter any whole number between 0 and 4,000. If you use an entry of 0, there is no menu display delay.
5.	Quit Registry Editor, and then restart the computer.