We don’t really know when there are some new file’s sit on our computer. There are possibilities to think the file can be a virus. whatisthatfile is a free online web tool which helps you to identify any unknown files on your computer.
This tool doesn’t cover all of the file types but still covers most of them. You can even add when you find a new file on your computer to the list which will help other users who visit this website.
Results will appear immediately as you type.
For example,
type - thumbs.db, you get the result as
Windows XP/2003 Picture Thumbnails Cache
Generated by Windows to cache the thumbnails of pictures in the parent folder.
This file is usually safe.
http://www.whatisthatfile.com/)