Updated Amazon's Kindle for PC app is now available to world+dog.

The über etailer first unveiled the app last month, at Microsoft's Windows 7 launch in New York City, and now you can actually download the thing.

You can download etitles even if you don't own the physical device. But if you do own one, it will automatically synchronize with the Windows app - or the iPhone app - via its built-in wireless connection. If you've read to a particular page on your physical reader, for example, that page will appear when you open up the PC app.

The free Kindle for PC runs on Windows XP, Windows Vista, and the new Windows 7, but it offers a few specialized hooks for Microsoft's latest OS, including support for Windows 7's touchscreen technology.

Kindle for PC arrives as Amazon arch rival prepares to launch its Nook - yes, Nook - ereader. Barnes & Noble already offers software for the PC, iPhone, Mac, and certain BlackBerries and Motorola phones.

Kindleware is still limited to the PC and the iPhone. But Amazon says a Mac version is "coming soon."

Amazon sells ebooks in the DRM-ified .AZW format and the unprotected mobipocket format on which AZW is based. The large-format Kindle DX also reads PDF files natively, but other incarnations of the device do not.

Kindle for PC can be used outside the US - in 100 countries, Amazon says - but the company points out that "book availability may vary" if you're not stateside. The company has yet to respond to a request for comment on which it how many titles will be available outside the US.

You can download the app here. ®

Update

Amazon says that "Content availability varies by country due to a number of factors. Each customer has a content catalogue associated with their region or country, and we display the appropriate catalogue for each customer."

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