Hi,
I’ve bought a pro license and I’m about to install Windows Vista and keep Windows XP on the same PC with multiboot for compatibility issues.
I wonder if I can install Avast on the two OS using the same pro license. (Or must I buy a second license or install home version on one of the OS ?)
Thank you for your answer.
I cannot be sure in my answer, that is why I just recommend you to read the license agreement. There always is the information about licensing conditions.
The license agrrement says :
You may: Install the Software in a single location on a hard disk or other storage device of up to the number of computers indicated in the license agreement.
So, are multiboot OS on a single physical PC (and are VMWare virtual PCs) considered as a single computer by Alwil ?
The primary user of each computer on which the Software is installed or used may also install the Software on one home or portable computer.
I’ve bought the pro version for my main home PC, can I install it on two home PCs if i am the only user of these two PCs ?
I cannot say for sure, because I’ve never seen the avast license agreement, 
but mainly one license is provided for one physical computer. That means that this license may be used at one single piece of hardware. If you have a hundred operating systems at your single computer, you may install a hundred licensed copies of the product there. But if you have two or more computers, choose only one of them to be protected by the product.
You could try sales@avast.com they should be able to confirm.
You can use one avast! Professional license in both operating systems, if they are installed on one computer.
You cannot install and use avast! Professional on more computers than licenses you have purchased.
Thanks a lot