The first to lose access will be Windows XP and Windows ME users. For them, compatible games (everything except MSN Go) will disappear in more days on July 31, 2019. Windows 7 users will have a short break. They will have access to Backgammon, Checkers, Spades and MSN Go until January 22, 2020, or about a week after Microsoft completes normal support for Windows 7.
There are likely to be web-based equivalents for these games, so you may not be completely stuck if you are determined to play something on an older PC. However, Microsoft will undoubtedly prefer that you upgrade to a Windows 10 system and play something from your own app store. If it is, it is almost surprising that the support has not ended before. Microsoft has a regular maintenance of Windows XP and more years ago: Internet games on those platforms lived clearly with borrowed time, and Windows 7 is not far behind.