If the computer fires up (the BIOS information appears and the floppy drive is accessed, but nothing more), you have some sleuthing to do. Follow these steps:

1. Turn off the computer, open it, and check the cables. Are the power and data cables attached to the drive? On SATA drives, be sure the SATA data and power cables are firmly attached to the drive. First-generation SATA drives don't use locking mechanisms on these cables, and they can be easily removed. If you recently installed a new piece of hardware or were mucking around inside your computer case, it's very possible that you unintentionally jiggled a connection loose. If you use an ATA/IDE drive, be sure pin 1 (marked as a red or speckled stripe on the edge of the cable) is lined up with pin 1 on the hard disk and motherboard. If you use only 80-wire cables, the cable is keyed, so it can't be installed wrong. However, older, 40-wire cables (often used on CD and DVD drives) are not always keyed.


2. Check the settings on the drive to be sure they are correct. If you have a SCSI drive, check the ID number and termination, per the instruction manual for the drive. If you have an ATA/IDE drive, check the master/slave settings and channel assignment. If you have two devices on the same ATA/IDE channel, both set to master or both set to slave, there will be a conflict. You can have only one master and one slave per ATA/IDE channel. You typically change the setting by using a little jumper block on the back of the hard drive, next to the data and power connectors (ditto for ATA/IDE-based DVD drives). Many recent systems use the CSEL or Cable Select setting for both drives. When used with an 80-wire 40-pin cable, the blue end of the cable plugs into the motherboard, the drive on the middle of the cable (gray connector) is slave, and the drive on the far end of the cable (black connector) is master. Note that many Western Digital hard disks do not use a jumper block if they are the only drive on the cable.


3. Check the BIOS settings by pressing the appropriate key during POST (Power-On Self Test) and having the computer autodetect the drive type. Be sure the drive is listed and recognized. If you have just upgraded to SATA hard disks, be sure the SATA host adapters on the motherboard are enabled in the system BIOS. On many systems, SATA functions are disabled by default. If you use a SATA host adapter card, or if the SATA ports on your motherboard use a third-party chip rather than being controlled by the motherboard chipset, you will need to install the appropriate third-party driver file before you can use SATA drives.