I've got some steam games that won't run on my current computer, but I bought anyway because they were cheap, or part of a bundle, or what have you. I figure I'll be getting a new gaming desktop at some point in the next few years, and the games won't be going anywhere in the meantime. The trick is getting a job that pays well enough for me to move out of my parents house and support myself. Once I pull that off, well, let's just say I'm pretty good at saving up for something I want.
Also the first time I bought Morrowind, it absolutely would not run on my computer. I managed to talk the clerk at EB games into taking it back, since it was used to begin with and I really couldn't do anything with it. My (family's) computer at the time was theoretically within the minimum requirements, but for whatever reason I got a black screen when I tried to play it. I think it may have been a driver issue, but I couldn't figure it out at the time. I wound up getting it again years later, on a more powerful computer capable of doing quite a bit more with it than that one could have even if I could have coaxed it into running on it.