Thanks Jeff,
 I tried the optimization last night and removed unwanted programs etc.
 The clunking seams to be there no matter what velocity I choose,but it is only there when the motors are running at their top speed.About once every second the motors have a loud clunk.At first I thought it was at a set point where the motor turns.Iam guessing the clunk can make it lose steps.
 I think smooth stepper might be a step in the right direction for me,so in a few days I will order one and see if it performs miracles for me.
 Thanks again
 Jason

 Well I ordered a Smoothstepper from Peter and the service is great.The postage was fast.My only problem is that I forgot to order the ribbon cable. I knew I needed one to hook it up and for some reason I thought the smoothstepper comes with both USB and ribbon cable.
 Iam a fool.It comes with a USB cable,not USB and the other one. Peter's website clearly says usb cable.
 Anyway,I will find other things on the mill to set up better while waiting for that cable.
 Thanks for the fast service Peter.
 Regards Jason

I received my new cable today for my smoothstepper and gave the unit a test run.
 Perfect!
 My clunking noise from the steppers has gone.Iam not losing steps any more.It just seams like a whole new machine now.
 I couldn't resist speeding things up,so I bumped the speed of the steppers from 200mm minute up to 1000mm minute just to see what it would do.Everything went well at that speed,but I dropped it back to 500mm minute to be a little safer.
 Tonight I have cut out several little helicopter parts from carbon fiber and others from Acetal with perfect results every time.
 Thanks Peter for a great product and thank you to the other guys who gave me good advice too.
 Jason