Thumb.db is is a cache of the current picture in that directory.to remove it go for following step1 > open "WINDOWS EXPLORER". 2>go to "TOOLS". 3>open "FOLDER OPTIONS". 4>go to "VIEW". 5>see 1st section "FILES & FOLDERS". 6>click on the "DO NOT CACHE THUMBNAILS". now the thumbnail file will be removed from ur computer once u do this the file will be never created....