I am running a Gateway desktop system with a Western Digital HDD which is running out of room. My OS is Win XP Home. I have a bay for a second internal HDD. I was wondering if a new, formatted Western HDD (40 GB) can be installed in this desktop system as a mere storage device, or when a second HDD is installed as a Slave the OS has to be installed on it also? I want to make use of this FREE (!!) HDD and not just purchase an external back-up drive for extra storage capacity.