I have dug a ditch 4 feet deep along side of my driveway that always flooded and turned to ice in the winter.Then I added about 4 or 5 inchs of new driveway material so no more flooding but my question is this. When it rains the ditch fills to the top at 1 end and over flows will a french drain help me and where will all the water go?
You're going to need an outlet for that water regardless of whether you have a ditch or a french drain (and in your case, I think you are describing not so much a french drain as a "diversion trench").
Digging a very deep ditch, as you have done, is not nearly as effective as digging a very shallow ditch that actually has an outlet of some kind. Eventually the ditch fills up, as you have seen, and if it is four feet deep, you need to outlet somewhere that is even deeper than four feet.