Hello Teressab,
Microsoft itself (thru its electronic distribution agent Digital River) is the ONLY entity authorized to sell electronically distributed (that is, having the product key emailed to you and then providing a download link to download the software) licenses for Windows and Office to end users/consumers.
So, any purchase of a Windows or Office license from eBay (or any other sales venue for that matter) that involves electronic distribution/delivery is by definition an unauthorized sale. Furthermore, Microsoft considers sales of its products on eBay (and other similar venues) regardless of the delivery method (electonic distribution/delivery, full packaged product, or OEM product) to be "secondary purchases," a classification that does not qualify as a sale from an authorized reseller to a consumer, and therfore does not qualify for certain benefits. For example, according to the Office 2010 Technology Guarantee (www.office.com/techg) FAQ, a purchase of Office 2007 from an eBay seller would not qualify one to receive the free upgrade to Office 2010 because eBay sellers are not authorized resellers http://office2010.microsoft.com/en-us/tech-guarantee/microsoft-office-2010-technology-guarantee-faq-HA101812304.aspx.
EBay and PayPal rules state that you can return any product purchased on eBay with PayPal if the product is "significantly not as described (SNAD)." In cases concerning the sale of product keys (which is not permitted by the Software Licensing Terms), your item would have been advertised as a "genuine" product but since it is not, it is Significantly Not As Described so you have grounds to open a dispute and return the item to the seller for a full refund. http://pages.ebay.com/help/buy/item-not-received.html
Buy Office 2007 Now, Get Office 2010 Free http://office2010.microsoft.com/en-us/tech-guarantee/microsoft-office-2010-technology-guarantee-FX101825695.aspx?CTT=97