|There is a .dat extension associated with VCD video files. The usual way to convert them seems to be to use a utility called VCDGEAR:|
but they only show support up to XP in x86 so I don't know if it'll work with your windows 8. And apparently VCD files are video and the conversion process converts them to MPEG. Since you're talking about still photos I doubt they are VCD files.
I seem to recall some dat files used in conjuction with picture files but they aren't the pictures themselves so as Jennifer asks, what did you use to create or store the pictures? Are they on some portable media--cd, flash drive, etc.?