i have two 40gb drives on my system. both show on startup, but then after awhile i hear this clicking noise coming from my tower, and then my slave drive doesnt show anymore. i'm thinking my slave may have become defected. any ideas?

Sounds like your slave drive "has given up the ghost". Unless you have a "clean" room, and I don't mean pick up your clothes clean, and if the information is valuable, you could move the platters into another, similar hard drive to retrieve the data. To bad it's not the HD external electronics. Easier to change out and recover the data. There are some hard drive recovery businesses out there, but they cost anywhere between $1,500 to $5,000, maybe less, haven't looked in a couple of years, to recover your data. Depends on what it is worth to you. Sorry for the bad news...