That is the old Windows Cardfile format. I still use it. I have carried over my .crd files from 3.X to 95, 98, 98Se, ME and now XP. It works perfectly so I see no reason to change it.
I recall there used to be a converter utility . . . search under Windows Cardfile. If I find it, I'll edit this.
BTW . . . the files are read by CARDFILE.EXE . . . only about 94 K.