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A reader writes, "My PC cannot detect my hard disk (sometimes).  And I suspect the CMOS has been infected by virus. What should I do?"

The inability of your system to always detect the hard disk is usually not a virus. Most of the time it is a sign that the hard disk is not always spinning-up-to-speed and may be an indicator that it is close to failing.   Now is the time to back-it-up!

eide1s.jpg (29803 bytes)Disk drives have a lubricant on the platters.  It may thicken over the years.  The heads can literally stick to the surface and prevent the drive from spinning.  You will usually see this problem, if it is the problem, when your computer has been off for awhile--usually in the morning when it is also cooler.  If it is really stuck and the drive won’t spin-up at all, you can pull the drive out of the computer and flex the frame a LITTLE by twisting it with your hands at opposite corners of the drive to pop the heads loose from the platters.  You may not see actual flexing of the frame.  The dimensions involved in this process are measured in microns.  Do not apply too much pressure to the top of the drive.  Do this at your own risk.

You could have a defective motherboard or a defective or loose IDE cable (the flat one).  The power connector may not be plugged all the way on. Sometimes one of the connectors in the power plug, the one which plugs into the drive, will pull part way back out of the plug and cause an intermittent operation of the hard disk. You can reseat it by pushing on the corresponding cable at the back of the connector.  Needle nose pliers are useful for this. You may have to pull it all the way out, bend the little locking tabs outward (I use an Xacto knife), and reseat it.   Or use a spare power plug.

Another possibility is that the drive is on the same cable with another drive or CD-ROM and it isn’t jumpered correctly.

Some hard disks from one manufacturer, especially older ones, do not work or work well or work at all with other hard disks from another manufacturer.   One may spin up and the other may not.  Try power cycling the computer with just one of them jumpered as a single master.  If is isn't bootable, boot on a bootable floppy and see if the hard disk is detected (or accessible) every time.   Finally, some hard disks (e.g., Western Digital)  are jumpered differently when used with certain others from the same or different manufacturer.  Try them.

I have not seen a virus change the CMOS, but I guess it is possible. There are many viruses that infect hard disk boot tracks and can cause boot problems; but, I don’t believe I have seen them cause intermittent drive detect problems.  You can down-load an evaluation copy of McAfee Anti-Virus at:



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