OK, let's get one thing straight. You are NOT going to get hold of an unused Xbox Live Microsoft Points code anytime soon.
Well, not without a little hard work on your part anyway.
Anyone online (and we mean, literally anyone and everyone) who says they know a sure fire way of getting hold of some free Microsoft Points is a straight up scammer trying to con you out of personal details for their own, sordid use. This is just common knowledge, officially backed up by Microsoft in various statements over the years.
The one legit way of picking up some free Microsoft Point, would be to take a look at Microsoft's Rewards program (the official website of which can be found HERE).
Users are rewarded with Microsoft Points in return for completing specific actions on Xbox Live. For example, buying select pieces of premium content on the Game Marketplace will warrant you a varying amount of Microsoft Points upon purchase. Oh yes, you have to put in to get out.
Nothing in this life come for free, and that is certainly the case with Microsoft Points. Be careful when coming up against any 'offers' that claim to be legit; they simply are not.