This one is an old but useful hack for making the Start menu appear as quickly as you click on it in Windows XP.
By default,a delay value of 400 is associated with the registry key of MenuShowDelay(HKEY_CURRENT_USER Control Panel Desktop MenuShowDelay).
To change this default value:
1.Open registry editor (Start>Run>regedt32)
(Backup the registry first before doing anything,refer to my earlier post on how to do that).
2.Navigate to HKEY_CURRENT_USER Control Panel Desktop
3.On the right pane,locate the key MenuShowDelay.
4.Double click on it to change the value from 400 to 0.
5.Save the changes and exit registry editor.
6.Click on Start menu and you will see that it has become super fast.
7.All done.
Peace.