http://www.amazon.com/gp/feature.htm...l_6g97entshf_b
That's the link for the Kindle reader for Windows.
Once you have it installed, look under the "Tools" menu for "Manage Your Kindle". That will take you to the Amazon site where you can search for "Retail Arbitrage", or any other Kindle book you may want. It's just like having a real Kindle except it's on Windows.
From that point it looks like a sale, but the price is zero. Just continue along like a normal sale and you will be notified that your Kindle reader for windows is downloading the book.
The above instructions assume you already have an account with Amazon. Everybody does, don't they?