How to add a third hard drive

To get away without adding any new PC cards it could be worth putting you new drive in place of you secondary drive, then coping the contents of the master to the secondary, power down remove master disk, replace wiht th new disk (making sure to change jumper to slave, reintodue the old secondary drive, and copy the disks information.
However if you want loads of disks you will need a hard disk controller card.

Just a side comment;
Make sure that you have enough power supply to handle all of your needs.
300 Watt is the minimum for adding a 5th drive.
I would consider upgrading to a 400 Watt if I were you.

If you don't need to access all drives at thesame time, you can replace your slave drive with either a hard drive selector, or a hot swap drive bay.
With either, I would assign high letters to the CD and RW drives so that the letters don't change as you add in drives.

Chas