All games are originals bought that I bought while in Japan. If you dont know what doujin games are, they are indie games made by small groups of people and sold in non-traditional game shops. All these are in like new condition and will run in Windows, all should run fine in Win7 with no issues, YMMV.
Original Suguri (a little war on brand new earth) by Orange-Juice. Great game, very challenging. Great soundtrack, hard to find. - $25
Original Qualia 3 ~multi agent~ by Shindenken. Great game, very fluid graphics where you evolve your vector based cell to different upgraded parts. Very challenging. Great soundtrack, hard to find. - $40