We have like 20 Office 2010 Product Key Boxes but we have no clue which one are used and which one are free.
Is there any way to check which one are free?
The best solution for this is to run a program called Produkey on all the machines currently running Office. Make a note of the product keys on each machine.
Next add all your Office keys into a spreadsheet. You then can match up which ones are used and which are available using a VLOOKUP
or something similar.