So, with more specific googling, I've discovered how to do it from a post here, for editions of Vista and Windows 7 that come with Group Policy Editor. (Unfortunately, GPE doesn't come with Windows 7 Starter, Home Basic, or Home Premium. If I discover the registry-equivalent, assuming one, I'll post it here.)
Here are my own detailed instructions, written against Windows 7 but likely the same for Vista:
- Run "**gpedit.msc**" directly using the Start menu. (You may also be able to find an "**Edit group policy**" control panel searching by name, but I couldn't find its icon listed anywhere under "All Control Panel Items". Go figure!)
- In the left-hand pane, expand User Configuration, then Administrative Templates, then Windows Components.
- Under Windows Components what was just expanded, select Windows Explorer.
- In the right-hand pane, sort by Setting, then scroll down and find the setting named "**Turn off the caching of thumbnails in hidden thumbs.db files**". Double-click it, set it to Enabled, and then click Apply.
- Log off Windows, and then log back on again.
Within Windows Explorer, you should now be able to delete the Thumbs.db files that you come across on the network (as long as another machine isn't currently locking the file), and the computer shouldn't create them again.
Also worth knowing: In Vista and Windows 7, Thumbs.db applies to network folders only. For local folders, Vista and Windows 7 instead save thumbnail cache information to a database in a local folder at "**%userprofile%\AppData\Local\Microsoft\Windows\Explorer**"
UPDATE: I just had to do this on another machine and was irritated by the steps, so I did a before/after comparison of a complete registry export. So, the registry equivalent for disabling Thumbs.db creation on network shares in Windows Vista and Windows 7 is:
Windows Registry Editor Version 5.00
If you place that content in its own text file (e.g. with Notepad) with a .REG extension, you can double-click to import on any Windows Vista or Windows 7 machine to apply the setting. Be careful editing your registry directly.