When using the start menu the you will notice a delay between different tiers of the menu hierarchy. For the fastest computer experience possible I recommend changing this value to zero. This will allow the different tiers to appear instantly.

Start Regedit. If you are unfamiliar with regedit please refer to our FAQ on how to get started.
Navigate to HKEY_CURRENT_USER\Control Panel\Desktop
Select MenuShowDelay from the list on the right.
Right on it and select Modify.
Change the value to 0
Reboot your computer.