I have three separate OSs installed on one of my computers, one XP and two Win7s. I have given each their own unique name.
For licensing purposes, does this count as a single ‘device’ or three ‘devices’?
Thank you for your help.
Each is regarded as a separate system so multiple licenses are required.
I have asked on a number of occasions for clarification on this and it is still as clear as mud.
The old answer of it should be OK for Multi boot or VM OS as you are only using one at a time - but that pre-dates the new link to the my.avast.com account. This sees the devices you have avast installed on and I’m fairly sure that it will think you have it installed on more than 1 system.
Yet they are still trotting out this old horse it ‘should’ as the license purchased still talks of 1 license for 1 PC for 1 year.
You have 1 PC (but 3 OSes) yet here are in the 21st century where multi-boot systems and multi VM OSes are fairly common. Yet we still have no clarity.
Thanks for your replies. Since there are different opinions on the subject, I decided to ask support directly. Promptly received a Ticket ID and answer:
I posed the question a little differently, mentioning that I have three computers, two with only one OS each and one with three OSs in three separate partitions. For licensing and pricing considerations, does this count as three devices, or five?
Answer: “For such cases, we consider it as three devices.”
I’m happy with that.
You’re welcome.
Hopefully you won’t bump into the multiple devices in your my.avast.com account that I mentioned.
Another forum volunteer and avast user has sought advice/clarification on this matter.
I certainly did. 
Hopefully Avast will chime in and give us a definite answer.