Yes you can mod your Xbox without those games, except that requires a hardware modification known as a modchip. It's a much more difficult operation (in my opinion) as you have to open up your Xbox and attach a physical device to it. There are a ton of modchips on the market all with various features and all that, frankly it's way too confusing for me, and I suck at soldering that's why the softmod solution is so good.
Check out Xbox Scene
for more information.