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Is there a way to make a USB flash drive not detected on a reboot, to avoid the PC trying to use it to boot from? Assuming you only have control over the flash drive and are not administering the PC. I know you can to disable it from the PC, and that there are ways to make the flash drive boot up an OS.

My problem, I have a portable apps drive full of useful stuff, but when I reboot I have to unplug and plug it back in or whatever PC I am working on at the time hangs.

A software solution would be best, but if anyone knows of a USB device that only becomes powered some time after boot up that would be interesting as well.

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If the computer is trying to boot from it even though it does not have a bootable partition, then there is nothing that you can do to change this fact.

With regard to your second possibility, that it will only get powered up if the computer is already booted, that is impossible. USB drives get powered up when the machine wants them to be, not any other time really.

Sorry, but it looks like you will keep having to pull it out every bootup (as people have been doing with floppies and CDs for a while now on some hardware).

Note: this assumes that you do not have access to the bios (as I inferred from the question that you only control the flash drive, not the computer).

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I disagree, a hardware solution would be as easy as a delayed switch. Like a device in between the PC and the flash drive that just says "Only connect the flash drive if I have seen a voltage on the PC for more than 30 seconds". All that said I haven't taken a multimeter to my PCs 5 volt rail to see if it actually drops when there is a software restart. – daniel Jan 25 at 4:13
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definately not nothing you can do. This is all controlled by bios. Just change bios settings and viola! – Matt H Jan 25 at 4:18
@MattH, and unknown person who seconded him. He explictly said that he can not do anything to the computer.. – soandos Jan 25 at 4:32
I was about to actually test out what happens to the USB voltage and realized I didn't need to get out a multimeter, restart your PC and watch the little red light on your optical mouse, it turns off and on again! I know this might be machine dependent, and if you have a powered USB hub in between it could confuse things, but I am guessing a huge number of PCs are setup the same way as mine, and stating that a PC restart will power cycle a USB device is not a giant assumption. – daniel Jan 25 at 4:36
Well it might or it might not (there are machines out there that are unable to boot from USB at all), but there is nothing that you can do to your drive that can change that. – soandos Jan 25 at 4:39
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You should not need to change any BIOS settings. Unless there is a password lock, you can use the 'select boot device' menu to boot from the hard drive. The usual key for this menu is F12.

Tip: If the BIOS flashes by too quickly, press Pause/Break to pause the BIOS.

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He does not have access to BIOS... – soandos Jan 25 at 5:12
The keys can change for different BIOSs. A PC I have on my desk only has the delete key to enter setup, and no quick option to pick the boot device. – daniel Jan 30 at 6:06
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If for some reason the BIOS settings aren't cutting it for you. You could look at actually installing a boot loader onto the USB drive.

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It might come to this, a boot loader that just says "boot off C:" – daniel Jan 30 at 5:52
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Well, its quite well documented on how to do it the other way, but i suspect all you need to do is turn off the boot flag on the USB drive with some partition editor like gparted.

As always, back up the drive before you do anything, since there's a slight risk of losing all your information

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This is the first nearly useful answer. I've checked the flags on the drive and the boot flag is not ticked. GParted looks like a great tool, the flags are written to the drive and not stored on the machine. It seems the windows OS just disregards the boot flag, I also ticked the hidden flag on the USB drive which had no effect. – daniel Jan 30 at 5:50
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The easiest thing to do is change the boot order in the bios so that HDD is first.

The computer won't look for other bootable devices once it's started booting from the HDD.

EDIT: You've now mentioned you cannot change the BIOS settings (or don't want to).

It's unusual that it sounds like it even attempts a boot process. You haven't been very clear on what you're seeing on screen. It shouldn't start booting a flash disk with just straight partitions on it. I suspect you have a partition maked bootable and an MBR or something on there that thinks it should boot from it. Have you had an OS loaded onto it before.

Otherwise, the BIOS initiates boot. The first thing that the computer will do is run the BIOS firmware. The BIOS may look at the flash disk. It should pass over it if it's not got an MBR record So unless you instruct the BIOS NOT to boot from a flash disk, nothing you do to it will make any difference. The BIOS may look at the disk to see if it has an MBR or similar and if it doesn't it should skip it moving onto the next device in the boot priority.

Someone has suggested pressing a key combination to select which device to boot first. However, IMHO that's just as much trouble as unplugging the drive and plugging it back in.

Can you check the drive doesn't have a partition marked bootable, and there is no MBR on there despite there being no OS is there? It should just be a straight partition.

EDIT2: Since the computer is hanging at "verifying dmi pool data". The following link may be of benefit.

Google: "verifying DMI Pool data freeze"

It's an extremely common problem.

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Yes but, this is for a portable USB drive I use on other peoples machines. Other people don't like me playing around in their BIOS settings, also if I have new 4 machines that I have to work on in a week I'd prefer to change the one USB device than the 4 machines. – daniel Jan 25 at 4:27
@daniel, you didn't mention this in your question. Your question is now extended to other machines on the network as well. Please update. – Matt H Jan 25 at 9:28
Or at least it wasn't clear what you meant by "administering the pc". Sorry. please read my comments in my updated answer. – Matt H Jan 25 at 10:25
I am fairly sure the MBR isn't my issue, if the BIOS has its primary boot device set to the USB and there isn't a bootable partition there it will just hang at "verifying DMI Pool data" – daniel Jan 30 at 6:34
@daniel - see this link it may be of help: computerhope.com/issues/ch000474.htm – Matt H Jan 31 at 23:30
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