Thanks you for the suggestions:
AlbertP- I checked in my BIOS and there is no section for NumLock.
Seppalta- I've used that resource before for other LXDE tweaks. It's very useful but I find nothing pertaining to NumLock in the autostart section. You have given me a better starting point though.
Thank you both for your quick replies, I'll keep you informed.
HP a6619f, 4GB ram, 500 GB HDD, Nvidia GeForce 930 GS
Mint 13 Cinnamon 64