Take the 2-minute tour ×
Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

At the first press of the power button to switch on the computer, the hard disk is not detected, BIOS says "unknown device" instead of hard disk. Then I switch off the computer by pressing the power button and turn it back on and then as if by magic, the hard-disk is detected and everything boots up and works fine.

I am forced to think that the hard-drive is bad, (I did change the hard drive cable with a new one but with no success).

This has been happening for a week and without fail, it always works the second time the computer is switched on. The switching on-off-on must occur one after the other with no or a few seconds time interval.

Why does it always work the second time?

share|improve this question
add comment

2 Answers

up vote 4 down vote accepted

Sometimes this is caused by the computer trying to boot before the harddrive has time to spin up. I believe this usually happens on drives which have many platters (due to the weight the motor takes longer to get up to speed), but that may be entirely incorrect ;-)

Usually there's a setting in the bios to add a delay before detecting the disks. I'd suggest trying there first.

edit: this article indicates it's actually due to ide drives taking longer to initialise. Same solution, though.

share|improve this answer
    
thanks will try and get back –  Doopy Doo Feb 9 '12 at 14:54
add comment

Check the bios for a quick boot (or similar) setting, turn it off, it should allow a more thorough hardware check when turned off, see if this gives the drive more time to spin up and stop giving you this error.

I agree, your hard drive may be dying a slow death of the spindle motor or bearings, back up your data and replace it.

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.