I tried Linux Mint a few years ago, it was really easy to install back then, but I'm guessing it's grown in size since. I think if I remember correctly running it off a memory stick and booting into that instead of windows just so I could test it before taking the plunge.
Also I think you can, or at least could dual boot so you could leave windows in place and either boot into windows, or into Linux. I assume that's still possible.
Hopefully all your software will run on it.