I've been having problems with my 2000 Rancher ES starting when it is below 40 degrees outside. When I took it to my dealer for the recent recall, I asked them to look at the bike and see if they could figure out why it wasn't starting properly. After messing with it for a day they came back saying that it is a bad CDI box, and that when my bike gets cold it's not sparking properly. My question is does anyone know what a CDI box is, and has any other Rancher owners had to replace this component on their bikes? I'm just a little disappointed due to the fact that my bike has less than 100 hrs on it, is less than a year old, and is already having components going bad.

The CDI module, is similiar to the electronic ingition in your truck or car. This is the first time I have heard of this problem.

So far 102 hours & 830 miles with no problems.

(knocking on wood)

CDI stands for "Capacitive discharge ignition"
It is probably one of the most reliable type of ignition systems made for ATVs, snowmobile and other applications. If your problem is no longer under warranty I would suggest that you try to get some kind of guarantee or other assurance from the dealer that replacing it will cure the problem. It is a fairly expensive part!
Some possible causes for premature failure are:
1. welding on any part of your quad or attached parts such as a plow or winch mount without disconnecting the unit.
2. Incorrectly wired accesories
3.loose battery connections causing arcing which in turn can result in voltage spikes. Any of these can cause failure but in the majority of cases it will result in a total failure of the CDI box. (Not a temperature related intermittent failure as you describe)