Until a few months ago, one would need additional software to get Windows Explorer to display RAW images shot with a digital camera on a 64-bit windows system. For example Canon and other vendors don’t bother to provide one for systems like these. In order to preview RAW images in the Windows Explorer one would have to buy software like FastPictureViewer.
But now happily enough Microsoft has filled this gap and provided the ‘Microsoft Camera Codec Pack’. They have released both a 32 and 64-bit package. You can download and read more about it here: http://www.microsoft.com/download/en/details.aspx?id=26829.