Thumbs.db was created in Windows XP in every folder that contained picture files.

Windows 7 creates a central thumbache in your user folder.

But Windows 7 creates thumbs.db files while browsing network folders.

Here is a little howto to disable thumbs.db in Windows 7 browsing network folders.

1. Open your registry editor.
2. Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\
3. If key “Explorer” doesn’t exists create a key named “Explorer”
4. In key “Explorer” please create a new DWORD 32 bit value named “DisableThumbsDBOnNetworkFolders” with value = 1
5. Reboot your system

Another possibility:

1. Download this packed registry file
2. Unpack the archive
3. Execute the unpacked registry file
4. Reboot your system.