The Helpdesk, LLC

Windows Vista introduced a new imaging stack, called Windows Imaging Component (WIC), and uses it in Windows Explorer to create thumbnails for most image file formats. 3rd parties can write their own WIC codec to support proprietary image formats such as Nikon NEF or Canon CR2 raw files and Windows Explorer is able to show thumbnails for those files when the corresponding codec is installed. Microsoft maintains a page containing links to existing codecs.

Sadly, there is no publicly available codec for the Photoshop PSD format but the newly released Microsoft Expression Blend 3 design tool includes such a codec so installing Blend 3 automatically installs the PSD codec. For those who don’t have a need for Blend and don’t want to install it, here is a little hacking guide to get the codec (a 256KB dll) and use it separately:

Get the codec and its dependencies:

Download the DLL below in the article attachments and save it.
Extract it to the %windir%\system32 directory, or any location that you prefer.
Register the codec from an administrator’s command prompt by running the following command: "regsvr32 %windir%\system32\PSDCodec.dll” (replace '%windir%\system32' with the location that you saved or copied the file to.)

 

Portions excerpted from http://www.ghacks.net/2009/07/29/view-photoshop-psd-thumbnails-in-vista-and-windows-7-explorer/.