I built this desktop but it's been about 3 years and I haven't worked with jumper settings since, so please bear with me. ASUS P4C800-E Del board. WD wd800jb C drive, of course jumpered to Master I went into Setup and found my CD is listed as Second Master (It is on a separate cable that hooks to the board in a separate socket from the C drive cable.) My existing wd2500jd (SATA) is shown as Third Master (jumpers on the far right set of pins) I'm trying to add another wd2500jd SATA drive, but the computer won't recognize it. It's currently jumpered to the same, far right set of pins (per WD, that's "Master" ) I've tried doing some research but could find nothing conclusive I could understand. I've got the drive I'm trying to add correctly cabled as far as I can tell. On the board, there are two SATA sockets. So far I've tried hooking the drive I'm trying to add to the second SATA socket in the pair where my existing sd2500jd drive is connected. It feels like it is running, but the computer can't recognize it, even with restarting. I tried connecting my existing SATA drive (E) to the other SATA socket and then when I checked Setup it showed that drive as 4th Master instead of Third Master , so both SATA sockets are apparently "Master" connections. When I did that I had the new drive hooked into the SATA socket where my E drive originally was (and where the E drive showed up as Third Master) but the computer still can't find the new drive. I've run the WD Lifeguard Tools drive installation program and it can't find the 3rd drive either, and it doesn't show up in Device Mgr. Don't know if this is any help, but my Device Mgr shows the C drive & the CD under "IDE Host Controller" and the existing E drive under "Mass Storage Controller" - but it doesn't show the new drive anywhere - I would think it should show up as a 2nd drive under "Mass Storage Controller"? The new drive is brand new, I bought it at the same time I bought my existing E drive but never needed the capacity till now so hadn't hooked it up before. Thanks!!