Originally Posted by Fardringle
Most new OEM computers include a 30 day TRIAL version of Microsoft Office, so unless you actually paid for a full version of office when you bought the laptop, you will need to pay for a license before you can continue using it.
This may reflect the situation. Office trial is often included with laptop bloatware, and it will work for 30 days or so, and users then decide to buy it or not. If not, they can delete it, or leave it on needing a key.
Belarc Advisor was suggested above. It is free, and when installed, it will show all installed/active keys. If there is no key listed for Office, you can assume it was never bought or activated.