This might be a bit of a strange one to start with, but the Xbox Game Bar isn’t just good for playing Halo 3. It’s actually got a really easy to use screen recording feature built-in and, if you’re using Windows 10, it’s free on the Windows Store.
Once installed you just hit the Windows key + G and the screen recording feature pops up.
Win+G it with Xbox Game Bar, the customizable, gaming overlay built into Windows 10. Xbox Game Bar works with most PC games, giving you instant access to widgets for screen capture and sharing, finding new teammates with LFG, and chatting with Xbox friends across Xbox console, mobile, and PC—all without leaving your game.