What causes my HDDs to swap on boot?

  jowoph 02:41 16 Mar 2009

I have a generic PC with Windows XP Pro (SP2).
There are two on-board hard disk drives (C & D) and a 500 GB USB Western Digital that I use for backup.
On three occasions recently, while booting the PC, I've received a message saying that HAL.dll was missing. The first time it happened it took me a while to work out that the PC had swapped drives C: & D: and was trying to boot from "my" D: drive, which it "thought" was C. Since then, when the problem recurs, it has been easy to enter BIOS and correct the settings but it's happened three times now (not on every boot, maybe once every couple of weeks) and I'm wondering whether this is due to a virus. I use AVG free version.
Any suggestions?

  Taff™ 06:07 16 Mar 2009

Are both the drives on the same IDE cable? If so check that the jumpers are set to Master and Slave and that the C drive is on the end of the cable. I`d also be suspicious of the CMOS battery. Does the computer time and date correct when this happens which might indicate it`s time for a new one.

If none of the above apply I would check the C HDD for errors. If it`s not spinning up quickly enough then the BIOS will not recognise it and it will go on to the next drive in the boot order.

  Shuffty 09:08 16 Mar 2009

Try here
click here=

  Peter 09:51 16 Mar 2009


Perhaps, as your BIOS seems to be affected, maybe your CMOS battery is running out. While you are using your machine, and for short periods of being switched off, the CMOS would be kept okay, but if you switch the machine off for a longer period the battery might run too low.


  jowoph 10:09 16 Mar 2009

Thanks for your comments, Taff.
The two drives are on separate IDE cables.
I think the CMOS battery should be OK since I only replaced it about 6 months ago and I understand they normally last at least a couple of years. The date and time are correct even when this problem occurs.
The second drive isn't mentioned in the boot sequence since it's not a system drive. My seuence is A:, C: then E: (a DVD drive).

  jowoph 10:15 16 Mar 2009

Thanks Shufty, for the Google links. The first time it happened I did follow such advice but in fact HAL.dll is not missing; the problem is that the PC "thinks" drive D is drive C and I suppose HAL.dll is probably the first file it looks for. If I place another copy of HAL.dll on what I've always known as drive D it tells me the next missing file!
The problem is easy to resolve via my BIOS; I just change the first drive to the drive mentioned in the second position (not in the Boot sequence but in the list of drives). But the problem is intermittent and annoying. So far it's ony happened three times but I suspect it'll happen again.

  jowoph 10:19 16 Mar 2009

Thanks Peter.
I don't think it's the CMOS battery though that's a possibility. I normally switch on my PC in the morning, around 7 a.m. and off at night (closing down properly) around midnight. So thre's never a long period without power. If (when!) the problem recurs I'll try replacing the CMOS battery but it's really fairly new - about 6 months old maximum.

  Taff™ 13:03 16 Mar 2009

Checked the C Drive for errors as I suggested?

  jowoph 14:46 16 Mar 2009

Hi Taff
Yes, I've used chkdsk to check drive C: and no errors were reported. But how can I tell if it's spinnng at the correct speed?

  lotvic 23:17 16 Mar 2009

Did you *save* the changes in the BIOS settings?

  jowoph 00:39 17 Mar 2009

Hi Lotvic
Yes, I saved settings with F10.
It's only happened three times - 24th Feb, 25th Feb and 15th March but it's intriguing as well as annoying and I'd like to get to the bottom of it if I can.

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