Windows XP and Vista users will still be able to play their current games but they will no longer be able to download new games, view achievements, or use Origin's social features. More details can be found at the EA Support website.
Origin no longer supports Windows versions earlier than Windows 7. If you're running Windows Vista or older, you'll still be able to play your games, but you’ll need to upgrade your OS to enjoy all Origin has to offer.
What you'll still be able to do:
Play your current games Redeem codes Make in-game purchases Visit the Origin Store online Change your account settings online (Origin Access members) visit and add games from The Vault online
What you will not be able to do anymore:
Use the Store tab to browse and purchase new games (and The Vault, for Origin Access members) View achievements Change your account settings in the Origin client Download games Use your friends list and related features Chat and video chat View and edit your profile