MicroDicom

MicroDicom is a free DICOM viewer for Windows.
MicroDicom is application for primary processing and preservation of medical images in DICOM format. It is possible to open DICOM images produced by medical equipment (MRI, PET, CT, ...). It is also possible to open other image formats - BMP, GIF, JPEG, PNG, TIFF, ...
It is equipped with most common tools for manipulation of DICOM images and it has an intuitive user interface.
It is free to use and easily accessible to most. It has also been used by the U.S. Department of Veterans' Affairs to get medical data on their state of health.
References.
National Cancer Institute, DICOM viewer Links, "MicroDicom" https://wiki.nci.nih.gov