Key Management Service (KMS) is a legitimate Microsoft technology used by large organizations to activate volume licensed versions of Microsoft Office and Windows. Instead of each computer connecting to Microsoft’s servers, they connect to a company’s internal KMS host.
Someone downloading such an activator often encounters:
Here’s an article that explains what KMS activation actually is, why fake activators are dangerous, and how to legally activate Microsoft Office 2010.
If you own a valid product key:
If you don’t have a key: