You should not have any trouble installing a second HDD with XP Pro. Simply place the drive in the machine having made sure the jumper is set to "Slave". Then connect the drive to the slave connection of the IDE cable that your original disc is connected to.
XP should find the disc automatically and sort out the formatting etc for you. Just follow the on screen prompts. It will need formatting to NTFS, not FAT32. XP will then allocate a drive letter accordingly. You may find that if you have a DVD and a CD etc it will give the partition the next available letter, ie F:\.
You can then use the drive as normal as it will show as a drive in My Computer, Explorer etc. If you then want to partition the disc further you can do.