Dual Boot With Win XP - Debian First?

I want to dual boot windows XP and Debian.? I've seen the guides, but they all recommend that users have Windows XP installed first, and then install Debian.? This allows you to set it up with the default Debian installation to use GRUB / etc. and dual boot.? However, I won't have a copy of

Using Debian Package Manager

I just installed Debian.? I'm wondering about the Synaptic Package Manager.? As I've never used a GUI for Linux before, I will need to get used to how things work. I wanted to install a motherboard monitor.? I found one in the list, xmbmon, and chose to install it.? It said installation