Determine file type in windows

TrID may help you identify those files.

1. Download the program and definitions.
2. Place them in some directory.
3. Add that directory to the PATH:
   • Press Win+R,
   • Type systempropertiesadvanced, click OK,
   • Click Environment variables... button and look for PATH in the lower box,
   • Add a semicolon and TrID's directory.
4. You're now able to run TrID by typing trid in the command line. Examples are available on the program's site.

Some files have their type defined in their innards (it's called a magic number). For example, all windows applications and possibly all DLLs have first two bytes MZ. So sometimes you need to look in HEX editor to tell what is what. Example:

If you can, go download shareware Total Commander, place cursor over any file and hit F3 (View).

But sometimes even that won't help, especially with custom file formats some company might produce, but I hope this helps you a bit.

You can install kind of a un*x layer via the cygwin environment, and then use the file utility (included in package base), which checks the magic number of a file and can also give some additional informations:

$ file *
img234.png:         PNG image data, 834 x 354, 8-bit/color RGB, non-interlaced
folder:             directory
animation.flv:      Macromedia Flash Video
charmap.pdf:        PDF document, version 1.4
charmap.tex:        LaTeX 2e document, ASCII text
song.mp3:           MPEG ADTS, layer III, v1, 128 kbps, 44.1 kHz, JntStereo
dvd.iso:            # UDF filesystem data (version 1.5) 'HOLIDAY_SLIDESHOW              '

Indeed, cygwin is rather a over-motorized solution (minimal installation around 20MB) just to run one command, but then you also have a sophisticated CLI... one of the things I miss the most in Windows.