I have Windows 7. I actually tried to install it again while writing the post, and the same thing happened, but after I had posted the question, it decided to make a fool out of me and give me the option to install. Glad I solved the problem, but it is now running extremely slow in 3D mode, something that didn't happen before. I have a 7 GHz processor, and plenty of space. Maybe not enough video memory? Don't know what that means.