I think you're confused about what a crop factor is. The first thing you need to know is that a 50mm lens is a 50mm lens is a 50mm lens regardless of what it's mounted on. The difference is the field of view.
If you mount the M 50/1.7 on a film body that takes 35mm film, the FOV will be roughly 'normal', IE neither wide nor telephoto. When you mount the same lens on your DSLR (which has a crop factor of ~1.5) the field of view (or the angle of biew if you prefer) will be narrower, you will have a short telephoto lens.
If you use film as a basis for comparison (as most still do) then to work out the effective FOV you multiply by 1.5. This is the part that people get confused about. What it means is that your 50mm lens WHEN MOUNTED ON YOUR K10D will have the same field of view as a 75mm lens mounted on a film body that takes 24x36mm (135 or 35mm) film.
A side issue that confuses people is image circle. New designed-for-digital lenses like the DA series do not
generally have a large enough image circle to cover a traditional frame of 35mm film. If you put your 18-55 on a film body you will see severe vignetting, the corners will be completely black.
Matthew
EDIT: And of course someone's beaten me to it.