Back in the dark days of XP, when different programs had their own print managers, I could load things up into an image editor, crop it square, then tell it to print me a 2 inch by 2 inch photo. Easy peasy.
Now every time I try to print, no matter what the software, I get sent to Vista's miserable fucking photo printing wizard, which lets me print only a handful of sizes, most of which don't come with dimensions. How big, for instance, is a "wallet size"? Apparently it varies. When I dig into their
It's a perfect storm of stupid. First they reduce the functionality, and then they act as though their now-lobotomized print functionality is a great new feature. It's like when a chip company puts less chips in the bag and calls it "Low Calorie".
There may be some kind of work around that lets you tell Vista's crappy wizard to take a hike, but I was able to get around it using Paint.net. First resize the image to the size you need (the DPI defaults to 72 dpi, but that's horrible for printing. Set it at something like 600), then use the Canvas Size command to put your shrunken image into a 4x6 background. Then you can print it as a 4x6 photo, and your actual picture will be the size you need.
I suspect this may be part of Microsoft's plan to take moderately informed users and frustrate them so much with Vista's infantilizing enhancements that they become expert users, at which point they will uninstall Vista and use something else.