It has been my experiance that once hard drives start acting up they never run the same again, and even if you can get the mobo to see it do you want to take the chance on it's performance, data loss, that clicking sound is more than likley the ( dont roast me for not recalling the actual name) needle that reads the disk or the disk/s itself are not spining right, Now you have two things to ask your self do I spend more money than the drives worth and have it fixed, or do I get a new HD with double the space for the same amount that it would cost to fix the 40gb, this however depends on 1) is the 40gb the drive that holds your OS, if so do you have a recovery disk, or a legit copy of your OS 2)if not are you willing to shell out for a copy of your OS (hopefully your not running a Mac where OS are extremly high priced) or with the cost of a new drive and the cost of a OS (In Canadian dollars) around $500.00 do you spend a little more dough and get a whole new tower, the prices have droped as of late and for that kind of cash you can get a good system