It can run games, but very low end and non-demanding games. What kind of games are you intending to play on this build? And if you are considering on upgrading this build for gaming later on, I suggest stretching the budget a wee-bit more for a higher power supply...so it can be future proofed for adding in a graphic card.
Like I said before, I don't know how strict your budget is.
And no, you cannot use the same OS disc for two different computers. It's illegal. One OS disc = one license for one computer only.