Assuming you're already running a PC with a desktop OS, you can use virtualization to 'get your toe wet' and try linux without diving in entirely with a real install. On windows virtualbox is free for non-commercial use and pretty simple to set up.

If you've got a spare drive then install it on that leaving your existing install alone, or if you have spare space on your existing drive you can shrink a partition (backup important data first) and set up a multi-boot