I voted for LINUX! You don't have to be a computer expert to use LINUX, no no.... This was the case 10 years ago, not now... To install something on Linux (Fedora for instance) is as easy as installing for Windows. Not to mention that you can get Linux for free and all software is free as well. You have Open Office, visualization software, mathematical software. And you don't get computer viruses
It may be good if you add another option in the poll: How about Mac OS

Mac OS is just great!!!
If I have to choose the order of preference it will be: Mac OS, Linux, Windows