Windows Vista changes how cached thumb nails are stored. Instead of having Thumbs.db files shattered all over the hard disk, then a central database is used instead, which is located here (files are prefixed thumbcache_????.db):

C:\Users\ {User Account Name} \AppData \Local \Microsoft \Windows \Explorer

Note to clear the the thumbnail cache, one can use the Disk Cleanup wizard.

Note to disable the use of the thumbnail cache:

1. Click on the Start menu and choose Computer.
2. In the Tools menu click Folder options....
3. Select the View fan and find and tick the option Always show icons, never thumbnails.

Credits My Digital Life