Hi and welcome to the WTT forums.
If the intention is to format and reinstall windows because of a fault or faults with the operating system or software that cannot be resolved in a timely and cost efficient way....then you will need the Microsoft Office installation disc(s) and the product key.
It is not really feasible to save your existing MSOffice Suite in the way you suggest.
If however if you made a disc image, at a time when your machine was running fast and sweet and with no problems, (viruses or system faults) then you could fit a new hard drive and reimage to the state it was in when the image was made. If you do this then you should normally remove Windows from the old hard drive.
Otherwise perhaps you could contact the previous owner of the machine and get them to post you the disc(s)