Well it's all about editing the BCD. Done that many times making my own dual boot setups.
Now there is a hard way using the built in command line tool bcdedit and the easy way, a free app called EasyBCD 2.2
These tips will be using EasyBCD 2.2
1) Google this program and install it. Now worries it's a good program and doesn't install crap.
2) Run it.
3) On the left panel click the Edit Boot Menu button
4) At the bottom click count down from and select how many seconds you want the timer to click before it auto boots.
5) Click save settings.
Your done!
P.S. I use this tool to add an entry to boot from USB stick my Win 8 Pro

Also if your going to play around I suggest you use EasyBCD edit to backup your BCD to a USB disk.
Bob
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