First a quick shout-out to Photoshop Elements - I recently bought version 7 on Ebay for $30 - that's a minimal price to pay for great editing software. I love "actions" which are things you can download to automatically give your pictures a certain look (let me know and I can do a post on what they are more specifically) and I don't feel at all that I need the full-version grown-up Photoshop - Elements is meeting all my needs and I'm sure it can do lots more that I don't even know about.
So open up Elements and the picture you want to use. Tweak your colors to how you want them. Then crop your picture to a square - to do this click the crop tool and then there will be a drop-down box where you can choose 5x5 - that's a square (equal sides, equal angles - you know). Then drag the box over your picture to how you want it.