Unstable boot-device selection

Changing Boot Sequence for Future Boots

Enter system setup (see Entering System Setup).

Use the arrow keys to highlight the Boot Device Configuration menu option and press to access the menu.

Press the up- and down-arrow keys to move through the list of devices.
Press plus (+) or minus (–) to change the boot priority of device.

Put the hard drive first on the list.

I've done that, but it doesn't stay. It changes on its own; not every time, it may boot from the C: drive over the course of several restarts, and then go back to trying to boot from the CD drives.

BTW: Did you actually check the BIOS settings on the new mobo?

Hmmm...if the mobo has just been replaced, I'd expect it to have a recent battery, unless the tech just used the battery from the old board.. The battery is only ~$2-$3 at discount stores.

Under Boot Configuration Features, Removable drive is by default the first drive that it attempts to boot from and CD/DVD is default for second boot drive. So make sure that neither First nor Second is still set to Removable or CD/DVD. You might try setting First to hard drive and setting Second to "disabled".

Is this RAID 0 or RAID 1?

You might want to run the diagnostic tests on the hard drives. If either drive is failing (eg, not getting up to speed fast enough), it might "time out" and fall back to boot from the CD or Removable drive.

The motherboard is a new (refurbished) one, installed today by Dell. I was wondering about the battery, and I might decide to replace it; but this problem has occurred intermittently since the system was new.

When was last time you replaced the motherboard battery which holds the settings in BIOS?

If that battery is weak/dead, settings may revert to factory defaults which could put the CD drive back at top of the boot sequence.

Thanks for your help, BTW. It's mirrored RAID, RAID 1. I have run over 12 hours of hardware diagnostics on the two hard drives, they are as clean as clean can be. I'm not sure which BIOS settings you're referring to, but if you mean boot priority or hard-drive boot priority, yes, I have checked them and the tech guy who installed the new mobo today checked them and neither of us understands why after booting successfully into Windows several times, the system will decide on its own without any user action to select the empty CD drives to boot from.

Tap F2 -> Highlight boot sequence -> Hit enter -> Highlight Array_Volume0 or something -> Tap letter 'U' make it as #1 and hit Enter.

Highlight Onboard devices -> hit enter -> Highlight USB Controller -> hit enter -> Hit right arrow key and make the option as No boot. Hit enter

Now Press Esc(Escape) -> save /Exit -> Enter

Verify as answer if the steps worked for you

Thanks for the suggestion. F2 at boot time does not bring up a selection marked "Boot sequence". The closest items seem to be

- Boot settings configuration (Fast boot, Numlock, Report keyboard errors)

- Hard disk boot priority

- CD/DVD boot priority

-1st boot device: RAID ARRAY0

- 2nd boot device: Disabled

F12 shows the two CD/DVD drives as the top boot devices.

(I should mention that knowing if ___ is the answer will take a while for testing; this problem seems to come and go. Right now it boots into Windows; yesterday it didn't; tomorrow, ???)

Please mark the issue as fixed if its working fine.

And there's no option to set "USB - no Boot" in BIOS Setup. The only option listed in the manual for USB in Setup is:

USB Functions -  Enabled or Disabled (Enabled by default).

You don't want to disable USB or none of your devices will work, though you might want to look there just to see if there are any other USB options, like "no boot".

I still think this might have something to do with hard drive function. Go here and download free SpeedFan. You can't use it to control fan speeds on Dell PCs, so don't even try, but it has the useful feature of reading the SMART diagnostics for your hard drives. Let it test your drives after they've been on but idle for a while when your at the Windows desktop and see if SpeedFan reports SMART issues with things like Spin Up Time, Spin Retry Count, etc. etc.

I keep the SpeedFan icon on the task bar so I can monitor hard drive and graphics chip temps on my Dell. Note that most Dell's don't have a CPU temperature sensor, so SpeedFan can't report CPU temps.

Alternative option -> F2 -> Integrated Devices -> USB Emulation -> No Boot, This will change the setting so that it doesnt boot from USB devices.

RoHe and Ron - Apologies

@veejdeej -

I don't know what BIOS setup screens you're looking at, but none of the options you've mentioned are listed in BIOS Setup for this specific system, as shown in Dell's online manual for the 435T.

You can't generalize from one system to another. You have to look at the manual for each specific system before you make any recommendations. Otherwise you'll only confuse the OP, without solving the problem.

Thanks,

Run system for a while without external USB drives attached. If you need them, connect after boot, use them, eject properly, and unplug (or just unplug after machine is completely shut down should also be acceptable). Just don't boot up with them attached.

Also, like RoHe said, go into BIOS and in the "Allowable Bootable Devices and Order Section" only select the RAIDed drive(s). I don't have machine or manual but it should be like he already described. Even if it looks fine, save the BIOS settings anyway.

Basically, you are removing these external USB drives from the "trouble-shooting equation" for a while. Make system as simple as possible to eliminate possibilities right-off-the-bat.

Thanks for all the suggestions. I've run over 12 hours of diagnostics on both of the hard drives that make up the RAID system, including SMART tests several times (they just take a few seconds unlike the read and verify tests) and never seen a problem. There's a chance - a very small chance, but easy to test - that the mobo isn't getting juice reliably from the on-board battery, which could cause it to revert to its defaults. I plan to replace it and see if that makes a difference. Of course there could also be corrosion in the battery socket or a hundred other things, but I want to eliminate "dying battery" as a suspect. I don't think I will detach the external USB drives at each boot; I need them and even if it works, that is too much trouble. If I have to do that whenever I boot then this system is a time-waster and not a help to me. At some point I have to stop babying this thing along and get some work done. This morning it booted straight into Windows; I had this problem with a new mobo a couple years ago, and eventually it settled down, maybe that is happening here.