Okay, from what I can see on that model you should have an icon that looks like this in your system tray (next to the clock):
When you click on it a menu like that one (may not be identical) should pop up. The "Tap to click" option is the one you want to turn off (so it's not checked -- like in the picture). If it's not there try poking through what options you do get.
I did see one or two posts saying the drivers that came with the d630 didn't have the option to disable tapping, so unfortunately it may not be there. You might be able to install other drivers that allow you to if you wish to go to that effort. It seems the drivers for the d430 model have the option and work on the d630.
Here's hoping they've updated the d630 so that the option will be right there for you though. Let me know how that goes. (And thanks for the karma!)