I'd ask if it has a cable select option and are you using it with an 80 conductor cable and on the proper connector? It's also possible that the drive isn't spinning up fast enough to be detected and you'd need to alter the BIOS if possible to allow more time. This is generally done by adding memory check time or not using some sort of quick boot function. Another thing I've seen cause this is using the HD auto-detect function with each restart rather than having the drive detected and remembered...if that makes any sense.