This may be a very little help, but perhaps an idea worth considering.
Would it be possible for you to find an exact replacement for the motherboard that got burnt? If so, you should be able to restore your complete system, including the Microsoft office programs, from your backup.
Also, in a home office environment where software tools are very powerful and important parts of your productivity,
a total backup plan is needed. Because of the policy Microsoft has about how many computers you can use for installations, you need to consider having "clone" computers. That is to say, every computer must be a duplicate of the other even down to small hardware details such as the type of video cards used.
Why? Because in that case you could reduce the number of new installations by simply making a clone of your hard drive. Save one or two of your installations for a new system, if and when that is needed.
Although the above may seem to violate the letter of the law, it is not really a violation of law. You are entitled to have a backup system. The policy Microsoft has adopted is rather oppressive and some other terrible word I can't remember right now.