|Does it have a floppy drive, and is there a disk in the drive? Sometimes, the same problem can arise when CD/DVD is set first in the boot order (and a non-bootable disk is in the drive), but this is not common.|
Has the machine been moved around a bit? Sometimes internal cables (IDE cables, power cables, etc) can become loose, resulting in a bad connection. Build-up of dust/tarnishing of contacts can also occur. Open the case and re-seat all the IDE cables, all PCI cards, and RAM modules. Sometimes it's that simple.
Open up the case and try booting the computer. Use your ear to try to determine the source of these clicks (sometimes a short length of hose used like a stethoscope can help isolate the sound). Clicking from a hard drive is usually a symptom of impending failure, although I've never known a failing drive to click in a pattern like you described. The clicking is usually random at first, becoming more constant as the drive nears total failure.
Are you able to boot from a bootable CD/DVD? if so, you can download a bootable image file of the Seagate diagnostics disk (which works on most drive types). Burn the image to CD/DVD media and boot the computer from it. Run the diagnostics tests to determine the health of your hard drive.
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