I think OBS is the best free recording software to use. It compresses files so your recordings won't be large (ahem Fraps). But the only bad thing about OBS is that you have to fiddle with the settings, the settings will be different for every computer and if you don't know how the settings work, OBS won't be effective. You really have to know what you're doing. But I like Fraps as well but they do a poor job compressing the files, it gets way too large for my liking.