Not web related, but possibly of interest.
thumbs.db is a file that caches the thumbnails of images stored within a folder. There are tools for deleting these files, but they are often through the use of an application to be downloaded or installed. There is an easy way to do this without resorting to that, just by using the command prompt.
del *thumbs.db /s /ah
This will delete all files (and folders) ending in thumbs.db (e.g. myappthumbs.db), so don't run this if you are unsure (or run it in a folder other than C:\). The /ah parameter searches hidden files and folders as well (so you may get access denied on C:\RECYCLER)
Disclaimer: Be very careful with this as a typo could prove disastrous. Do not run this if you are not completely sure and don't have a backup if a mistake is made.