"By the way, I never figured it out, what the heck is the purpose of marking squares in minesweeper?"

Ok, this would explain things a little. Marking mines makes the game MUCH easier, and more fun. It isn't, however, about keeping track of the mines as much as it is about allowing you to use the Right-Left click functionality. The key, as someone else mentioned earlier, is that when you click the Left and Right buttons at once on a number, and the correct number of mines are flagged bordering that number (like 1 mine is flagged bordering a '1' squar), then all the non-bomb squares bordering the number will be cleared off. If you make a mistake and there are two somehow flagged, it doesn't uncover any squares because you are obviously in error. This prevents you from making mistakes, and makes the game go much quicker. I also find that it helps my thinking because I think of "finding mines" rather than "removing squares." Once I figured out this trick, I ended up hardly ever having to guess and getting much better scores. I would actually go as far as to say, if you aren't using the Left-Right together clicking, you aren't playing the game right.

If you doubt me on this, at least try it once or twice. You'll be surprised how much better you do.