There is a ruby installer for Windows http://rubyinstaller.org/ , so you can just install that and then do "gem install rails" from the command line.

I imagine this is good enough to get you started.

Once you are ready to move on and start developing on a unix system you can install Vagrant which will give you disposable dev virtual machines running Linux (which will likely be closer to a real deployment environment than a Mac would be). http://www.vagrantup.com/

Your other alternative is to install a full Linux distribution on your computer. Honestly though you are best off using Vagrant in the long run regardless of your primary OS simply to avoid various headaches. Probably even if you use a Mac.

One of the biggest problems for newbies is that filenames in Linux are case sensitive whereas on Mac/Windows they are not.

A Mac is by no means a prerequisite for using Rails. The screenshots might look a little different , but in most cases the important parts will be identical.