Linux

I disagree with dual booting at the early stages. I like dual booting (or even better a VM if that covers you) once you've figured out what works and what doesn't (assuming something vital is in the "doesn't" category); but, if you are trying to decide if it is right for you, I don't think it does you any favors to be able drop back into old habits so easily. My recommendation is drop a bit of money on a second hard drive, pull the windows drive out and install just Linux. See if it works for you, if your "must-haves" are running painlessly or not. You still have the safety net if things go REALLY badly of just popping in the old windows drive and changing your boot options in the BIOS, but you will be less tempted to just boot Windows every time you use the computer - until you really have to.

For a start, in practice you aren't likely to actually reboot and load into a different OS very often. You can't really give something new a fair shake while you are still spending most of your time somewhere else. Minor things, like how you like your system to look/work will just push you back to windows because it's easy and you won't ever look at the options to find out that it can do what you want (and likely more). Second, there is the pesky windows updates that likes to fuck with the boot loader.

This is really only advice for an enthusiast that really wants to try Linux. I know some will disagree - everyone's experiences are different, but it is definitely my preferred methodology and helped me make the leap.