Hi ricvic. Presumably you have entered BIOS by pressing the DEL key at bootup and not found the hard drive there. You could try resetting the BIOS to default settings. If that doesn't help, check all the connections are secure. After that it's possible that the hard drive has failed or been corrupted, it's also possible that the motherboard is faulty. The only way to tell for certain is by substitution, and I think the easiest way would be to buy another hard drive. They are optainable fairly cheaply, e.g. click here. You can then hopefully install Windows on the new drive, and connect the old drive as slave. You may also be able to use the makers diagnostic software to see if the old drive is recoverable.