The default installation of Windows Vista doesn’t support Canon’s RAW codec – CR2. Thankfully, Canon does offer a CR2 codec for Vista. Unfortunately, it only supports the 32-bit flavour of the OS.
For a 64-bit version, we have to rely on a third-party provider. Ardfry Imaging have notified us that they have a CR2 codec for 64-bit versions of Windows Vista and XP. They are in beta right now, and it looks like it will eventually be a retail product. However, if you are using a 64-bit OS and are frustrated by not being able to preview your RAW images, this looks to be the only solution for now! Canon is showing no sign of ever making 64-bit drivers.