Save Secondary , Destroy Primary !

Hi all

I have a Pentium D something and a gigabyte of RAM, 160 GB HDD…..it somehow its quite sluggish for its speed. I cant play counter strike on it, let alone any other heavier games ! So I decided to format it..

PRIMARY OBJECTIVE: FORMAT THE C DRIVE (Primary Partition) WITHOUT AFFECTING THE D DRIVE (Secondary Partition.

OS: Windows XP

Secondary Objective: You gotta explain this to a newbie.

Id really appreciate a step wise approach…I just want my stuff on the D Drive to remain safe…Any help would be eternally appreciated…Thanks a lot !