Maybe, if you don't want to get into a third party program, you could see if this suits you:
Start Regedit.
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 50. (You can try 0 - it will do no harm but maybe a little inconvenient)
Reboot your computer.