Microsoft Camera Codec Pack
One of the best things about digital SLR cameras and higher-end point-and-shoot cameras is the ability to shoot in RAW mode. RAW images give you uncompressed, data-heavy versions of your digital photos that can be used for intensive edits and adjustments without negatively impacting the image quality.
Problem is, "RAW" isn't a file format, and these uncompressed images vary in file type depending on the camera you're shooting with. Normally, you'd have to hunt down the appropriate RAW codec from your camera maker in order to view and edit these photos on your system. This free Microsoft Camera Codec Pack enables viewing of several camera makers' RAW file types in Window Live Photo Gallery and Windows Explorer on both Windows 7 and Vista (SP2 and Windows Platform Update are required) and Windows 7 PCs. It also creates .JPG copies of your source RAW images so that you can edit them in Windows Photo Gallery while still retaining the untouched RAW photo.
However, not all of the most-recent cameras' RAW format images are supported by the software, so it's best to check the list of supported models on the Microsoft Camera Codec Pack download page. Notably, many RAW-shooting DSLRs, interchangeable-lens compacts, and advanced point-and-shoot cameras released in the past year or two may have RAW format images that aren't supported by the codec pack--at least not yet. If you have an older RAW-shooting camera or a new camera that saves files in a long-supported RAW file type, you should be in good shape with this free codec pack. It's a handy "one-stop-download" that supports RAW formats that include Canon's .CR2 files, Nikon's .NEF files, Sony's .ARW files, Olympus's .ORF files, Pentax's .PEF files, and others.
Note: This link takes you to the vendor's site, where you can download the version of the software appropriate to your OS.