: Some vendors sell digital-only keys. Ensure the site offers a money-back guarantee if the key fails to activate, as these are often "scrapped" from old machines.

: 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.

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

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