Can anyone tell me how to deactivate the daytime running lamps on my 2002 Pontiac Grand Prix?

You can try pulling the DRL fuse but that will also disable the auto headlight system. Plus you'd have to control the headlights manually at the switch.

However, the link below has a fix you can try:

http://macgp.clubgp.com/howto/appearance/drl/drl.htm

BTW - Welcome to AF. Also, we have a Grand Prix forum. You probably would have received a faster response there. See link below:

http://www.automotiveforums.com/vbulletin/forumdisplay.php?f=386