From above link;
“Turn off Caching of Windows 7 Thumbnails in Hidden thumbs.db Files
August 23, 2009 / Fred Janssen / 10 Comments
When I’m working in Windows Explorer managing my pictures and music, Windows 7 by default generates a file called thumbs.db in the folder that I am working in. The thumbs.db file is a thumbnail cache. Wikipedia states that a thumbnail cache is a file used to store thumbnail images for Windows Explorer‘s thumbnail view. This speeds up the display of images as the smaller images do not need to be recalculated every time the user views the folder. I don’t like extra files that I don’t use cluttering up my file system, and I get annoyed when I can’t delete them since they are system files and potentially in use and locked by Windows. I have a fast machine and don’t pay much attention to the thumbnails anyway, so I decided to turn this feature off.
There are a couple of ways to turn off caching of thumbnails, one includes editing the registry and the other includes using the Local Group Policy Editor. I have edited the registry a million times and don’t mind doing that, but it doesn’t get any easier than using the Local Group Policy Editor. The first step is to log on to Windows 7 as an administrator. To start the Local Group Policy Editor, click the Windows 7 start icon and type gpedit.msc in the search text box and hit Enter. The Editor will open to the top-level Local Computer Policy, so you will have to expand the User Configuration item in the left-side pane of the Editor window. Drill down through Administrative Templates, then Windows Components, and click on the Windows Explorer item. Near the top of the list in the right-hand pane of the Editor window you will find the setting “Turn off the caching of thumbnails in hidden thumbs.db files” (see below).image
To edit this policy setting, either double-click on the title of the policy or click the link titled “Edit Policy Setting” to the left of the setting list after you select the policy. It is interesting to note that below the Edit Policy Setting link it indicates that the requirement is Windows Vista Service Pack 1. To change the policy, merely check the “Enabled” radio button and click OK (see below).
image Close the Local Group Policy Editor and you will notice that all of those thumbs.db files have disappeared.”