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With the introduction of 1080p HD video support in iTunes last spring, in many cases users now have the choice of two different HD resolutions when purchasing and viewing content from the iTunes Store. While not everything is yet available in the higher, 1080p format, in those cases where it is you may still want to download or use the lower-resolution 720p version to save disk space or play back content on older, lower-performance PCs. iTunes provides…
