Windows 7 is this legit?

[DotFifty89]

Hi looking to buy windows 7, the description reads:

Windows 7 pro OEM with service pack 1 plus coa license product key dell disk.

Its £36

Does this sound ok? And will it work just like normal? I don't know a lot when it comes to operating systems but dont fancy paying around £75 for it.

 

[DotFifty89]

Apparently its from an old system which has been decommissioned, I thought it sounded a bit strange. There are hundreds of people selling it at around this price with similar descriptions, and have had hundreds of sales.