What’s the difference between an Xbox 360 Arcade and a normal 360 with a 20Gb memory apart from the memory?

I recently bought an Xbox 360 Arcade with Halo 3. I’ve gone over many websites trying to find differences between it and a normal 20Gb Xbox 360, or is that just it. If that is the case, cheap Levitra then will it play Xbox original games if I buy a 20Gb memory for it? Any answers would be greatly received.