Windows 7: How Windows Licensing Works?

I have purchased 10 licenses for windows 7 and have installed windows 7 on 10 laptops. Lets say I Install windows 7 on a 11th laptop, will windows 7 be valid on the 11th laptop, if atleast one of the laptops with Win 7 is turned off? In other words is Windows licensing concurrent? Or can I only install win 7 on 10 laptops whether the laptop is turned on or not? Any info will help me out. How does the licensing work?

Retail licenses can migrate to the machine of your choice as long as the installation on the previous machine is deleted. When activating the new install you may be forwarded to phone activation to be asked how many machines the copy is installed upon, to which the only accepted answer is one. This gives MS Activation servers the go-ahead to deactivate another machine which later appears online with that Product Key.

To delete Windows 7 use the booted Windows 7 DVD Custom install>Drive Options>Delete, a bootable partition manager like free Partition Wizard CD, or Diskpart command to Delete Partition Override from DVD or Repair CD: DISKPART At PC Startup

Every year at my job we like to reformat our laptops hard drive and re install the OS. When doing this with Win 7 do I just need to delete the partitions when reinstalling the OS or is there additional steps to take for licensing purposes?

Doesn't really matter. A reinstall is rarely a problem since it uses the same hardware signature stored in MS Activation servers for your Product Key.

Always boot the installer for installs, so you can use Custom install Drive Options to delete, repartition, and/or format the target partition, or not.

Here are tips for getting a perfect reinstall of Windows 7 based on thousands helped with here: Reinstalling Windows 7

Once you get the perfect reinstall, save a backup image as shown so you never have to reinstall again - just reimage the HD in 20 minutes from stored image, the modern way!

Thanks for the advice!