I bought theWindows Explorer Pro version 3.0. Depending on your playing strength you may or may not be happy with this program. If you are over USCF 1800, the opening are simply not detailed enough and it lacks a games database. However for the price it is a bargain and a great help for players who want to learn about the openings. A typical chess book on one opening retails for about $25 these days so this program could be used as guide for finding an opening you like then buying some of the more expensive products on the market. The portability is also nice. If the author keeps enhancing it, I think he has a real winner here. The technical support is excellent and the author seems to be very intent on improving it. I spend much of my time playing on chess.com with my iPhone and my Kindle Fire. This is mostly because I have a huge laptop and I am too lazy to lug it around. This product does not run on the Android operating system but this is often the case with iPhone software. Having both operatating systems, while Android has a number of fairly decent chess playing software, it is clearly lacking in what I call chess support software, primarily in chess databases and in products like this. By the way, the author is a member here on chess.com as well. The product has a fairly wide ranging opening library, a quiz feature and the latest professional version contains a chess engine which allows you to play against the opening you select. At $5.00 it is a bargain. He also has a version called Windows Explorer Lite which can be downloaded for free. If you have an iPhone 3GS or later or an iPod, give it a try.