[bwood]

Lets get some lingo straight:

DRL-Daytime Running Lamps:
This is a feature that has been standard on many GMs since the late 90s. The come on to help to make you more visible to oncoming traffic. It turns the low beams on when the parking brake is released. On some manual tranny models, the DRLs will be on anytime the parking brake is released. On most auto tranny models, they come on when the truck in put in gear or with the parking brake off (depends on the model/year). Usually there is a fuse that can be pulled to disable the DRLs.

The "Auto Headlights" feature:
This feature came out on the NBS trucks in 99 and other models around the same time (my 99 S10 had this feature). There is a photocell mounted in the dash (in the center of the dash in the defrost vent, some are flat and some stick up in a bulb shape-I believe this is on the models with the temp/compass in the rear view). This photocell is similar in function to the one on the outside of your house that turns on your security lights. It sends a signal to the control modual automatically turns on your light. You can override this by turning your headlight switch to the left once and from there you will have to operate them manually.

It sounds like you want to stop the DRLs. You should be able to accomplish this by pulling the fuse as stated earilier. If all of the lights come on like it is dark out even when it is daylight, you need to check and make sure the photocell has not been pushed into the dash or has something covering it. At work we have a 04 HD that got the photocell pushed into the dash by the guy who drives it putting his clipboard and paperwork on top of it. I put it back once (PITA) and he did it again. His boss said that since he keeps knocking out, he can start buying the bulbs that are buring all the time. Hope this helps.