I've had this happen to me, too. You get a new computer with a new OS, and your old games don't work. Sometimes, they will upgrade them, but sometimes they won't. I never did find Tetris for my Mac, but I found similar games. I Googled games for my OS and then read the descriptions. Often, they let you download and try them for a little while before you register and pay for them. One of my favorites with my old OS was Firefall Arcade, which they didn't upgrade for my new OS. I was so addicted to that game that I wondered how I'd exist without it, but I did. Now I have Majong Solitaire, which is popular enough that it comes in many forms, so maybe you can find it for a PC. I have something called Mike's Arcade, which has a number of games like the ones popular in the '80s: a version of Pac Man, Q Bird (which is like Q Bert), and some shooting games I don't play much. I really like Q Bird. I also have BoxXikon, where you stack squares and they disappear when there's a lineup of 3, trying to not fill up the board. Another with the same principle is faster, Descender. Downfall is another similar one. I know these aren't the high-tech games people play now, but they are relaxing and just my speed. Actually, I got so into Q Bird that I started some self-analysis based on how I played the game and what personality traits prevented me from being more successful. I even wrote up my little Q Bird philosophy:
1. Be careful. Don't be impatient or hasty, or you won't last very long.
2. Live within reality. Don't base your moves on what you want to be true but instead on what is.
3. Each board, don't worry about how many lives you still have left. Make every move count.
4. Don't start a game thinking, This time I'll make the high score list. The pressure means you usually won't. Just start playing with no preconceived notions or plans about what will happen.
5. It's OK to establish patterns that usually work, but if they don't this time, it's imperative to break out of the mold and try something different without delay. Don't get so hung up on doing things like you did last time that you can't change if those patterns won't work for this game.
6. When you start a game of Q-Bird, don't think about a different game you'll play next. Play Q-Bird now, and then you can switch games. If this is impossible, quit Q-Bird and play the other game.
7. Don't get so anxious to land on that one last square or egg that gives you an advantage that you forget about the worms and lose a life. It might be your last life, and the game will be over.