How do you fix an error 100 on a SWF embroidery machine?
On the back of your machine is a silver-colored wheel. There are a bunch of numbers on it. You need to turn the wheel until you can line up the 100 (it's in a red area on the wheel) with the red line on your machine). Turn on your machine and it should be just fine.

Sometimes after you fix a #100 error you'll get a #300 error. To fix  the #300 error, there is a silver knob on the right side of the machine, just behind the head. You'll need to gently turn it until the error stops - usually there is some resistance as you turn. The resistance will stop when you get it aligned.