If you need a key for legitimate use:
A legitimate Microsoft Office Professional 2007 product key is a 25-character alphanumeric code. It looks like this: XXXXX-XXXXX-XXXXX-XXXXX-XXXXX
It is vital to understand that Microsoft ended all support for Office 2007 on October 10, 2017. This means there are no more security updates, bug fixes, or technical support. Using an Office 2007 product key on a computer connected to the internet poses a significant security risk. Hackers often target unpatched vulnerabilities in older versions of Word and Excel to deliver malware.
Microsoft 365 Free Web Apps: You can use Word, Excel, and PowerPoint for free in a web browser with a basic Microsoft account.
Many cheap keys are stolen from MSDN (Microsoft Developer Network) subscriptions. These keys were never meant for resale. Microsoft periodically blacklists these keys. One day your Office works; the next day, it says "Product key invalid" and enters reduced-functionality mode (read-only).