: Often the most common source for physical "Product Key Cards" (PKC) or discs with keys. Look for sellers with high ratings and original physical packaging to increase the chance of getting a genuine, one-time-use key.

If you are buying a key simply to have a word processor or spreadsheet tool, consider these more secure and modern options:

: Websites like eBay or specialized software discount sites often sell "surplus" keys. These are frequently Volume Licensing (MAK/KMS) keys or OEM keys intended for specific hardware, which may violate Microsoft's Terms of Service if sold individually.

: A free, open-source suite that can open and save Office 2010 formats (.docx, .xlsx) without requiring a product key.