Ok, drive wiper didn't help much.
With much trepidation I went into the bowels of the machine with 'command prompt', found the $recycle.bin and deleted it' and everything in it. That got me back a little room, but the c drive is still filling up faster than I am adding data.
So I deleted a couple of programs (Dell assist and Google Earth). Not my first choice.
I read that I pads were having a similar problem, no room on the C drive.
I could try a Windows clean install, way past the trepidation stage.
If anyone has a better idea...
Glen