HELP! Using DBAN to wipe hard drive, selling computer, am I doing the right thing?

Hi,

I'm selling my Dell Inspirion 6000 Laptop with Windows XP on eBay and would like to make sure my hard drive is securely erased. The instructions are very confusing. So far I have downloaded DBAN, opened it, clicked to install it to the E:/ drive (a 2 gb flash drive). I've tried to decipher these instructions but I'm still confused. Do I need to do something with a CD or not since I'm using the flash drive? It's unclear whether it's one or the other, or both things that you need to do. Also will I lose the operating system completely? I want the hard drive wiped but I would like it to still have Windows XP. Is everything self explanatory once I restart the computer with the flash drive in or am I missing something??? Any help is really appreciated, thanks!