SERIOUS QUESTION: How to do a clean install of Windows 10 on laptop?

If you do not have the MS Office key, that could be a problem. If you upgrade from W7 to W10, you would not need the MS key, but if you clean install you would.

If your version is 2010 or earlier, you can get the key from existing installation using produkey. If it is 2013 or later, produkey cannot get office key as it is encrypted.

In the end, you have to keep a record of keys.