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Before you tell me to google around, trust me I did and nothing worked for me. I must be missing something.

I have a small PC with limited storage options. I have a small internal hard drive and 8GB usb stick. I can't fit the Windows XP install on the internal hard drive. So I'm trying to install it to the usb stick and make it boot.

BIOS recognizes the usb stick, also the Windows installer listed it in the partition list. It said I need to make MBR on the internal drive and use it to load OS from the usb stick, so I confirmed that, it copied some files etc, standard installation. But then after reboot I get the loading bar and after a second or two I get a BSOD with stopcode 0x7B (INACCESSIBLE_BOOT_DEVICE).

I checked the usb drive on another computer, the windows folder etc is there, partitions look alright. Next I checked the internal drive from linux liveCD, there is pretty much just 3 important files, ntldr, ntdetect and boot.ini.

Now, the boot.ini says: multi(0)disk(0)rdisk(0)partition..., I'm not sure if there is some special way to address usb partitions but I couldn't find one.

Looks like the bootloader on the internal drive is just unable to mount the usb stick and start the system. Although for that brief moment of time before BSOD the stick's led is flashing, but that might just be some BIOS usb initialization.

I got an idea to maybe use a different bootloader (grub?) on the internal drive but I'm not sure how to do that.

Any advice and pointers are appreciated. If you have any questions about details I left out, please ask in the comments and I'll try to answer.

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Sounds like a problem with an AHCI driver or something like that. Is that drive you've got the bootloader on in IDE mode? You'll often get that exact error on an internal drive if you install Windows in IDE mode and then switch to AHCI mode, so I'm guessing maybe your system is running AHCI and it won't play nice with the USB key...this is all conjecture though. – Shinrai Apr 14 '11 at 17:23
@Shinrai: The internal drive is a ATA Flash disk. I can't find anything about mode in BIOS... – jdbui Apr 14 '11 at 17:44
Nice article here, not sure if it works for flash drives, – Moab Apr 14 '11 at 17:44

An easy way to make your USB drive bootable is to use EasyBCD. It's a utility that takes care of all your boot issues. I have used it to make a bootable USB drive as well as setting up a dual boot on my computer. It doesn't do anything you can't do manually, it just gives you a nice interface and does all the hard stuff for you. Best of all, it's free. You can find it here:

share|improve this answer
Its not a boot issue as much as it is XP was never designed to install on a USB device, bootable or not. – Moab Apr 14 '11 at 17:48

check out,1113.html this is a great article on how to boot windows xp service pack 1 from usb. very easy to use and I would definitely recommend!

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Welcome to Super User! It would be nice to include the essential parts of the answer here, and provide the link only for future reference. – slhck Feb 16 '12 at 19:03

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