Assuming you have legally obtained a valid product key (from a genuine Microsoft certificate of authenticity), here is how to proceed:

Even though Visio Premium 2010 is over a decade old, many organizations still rely on it for legacy diagrams, process flows, and engineering schematics. The product key is the alphanumeric string that proves you own a genuine copy. Without it, you cannot:

If Visio Premium 2010 is already installed and activated on a machine, you can extract the key without reinstalling. Below are two safe, free, and widely trusted methods:

You might find a key, but will the software work?

If the product is no longer supported in your region, Microsoft may issue a re‑issue key or guide you toward an upgrade path.

Strictly speaking, this violates Microsoft’s licensing terms, but some reputable resellers on eBay or Amazon Marketplace sell "New Old Stock" (unopened boxes) of Visio 2010 Standard or Professional. Be wary of "Premium," as it was rarer. If you buy one, ensure the seller has a high rating and the package is factory sealed.