When you are purchasing MS Office its always been the case that if you purchase the OEM version with the computer (original equipment manufacturer version) the software is locked to that computer and can't be transferred to another new computer when it gets replaced. If you spend sometimes as little as $5 more and purchase the retail version from Officeworks or your local computer store you can install that on your new PC when it comes up for replacement time.
Remember that you can only install retail version software on one PC at a time, there are lots of other purchasing options if you need something different.
Microsoft had a go at changing that licensing for office 2013 but then pretty quickly changed back to what we have traditionally had in the past see here for more details on that:
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Digitalwelcomemat provides IT consultancy and services for business customers on the NSW Central Coast in Australia.