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Windows 7: Made bootable USB but getting "Disk read error" at boot time, why?

17 Oct 2011   #1

Windows 7 Professional SP1 32-bit
 
 
Made bootable USB but getting "Disk read error" at boot time, why?

Would greatly appreciate some help trying to create a bootable system on my 16GB USB stick. Here's what I did:

In Diskpart:
  • clean to wipe the USB stick clean
  • create partition primary offset=32 align=32 to create a fresh partition starting at sector 64 (rather than 63)
  • active to make it bootable
Next, I formatted it as NTFS with a 32KB cluster size. I then used
  • bootsect /nt60 U: /mbr
(where U: is my USB stick) to write boot code compatible with Vista/7's bootmgr.

I extracted the contents of a known working WinPE .iso image to the USB stick which placed a bootmgr and Boot\BCD in its root.

After restarting my computer, USB stick (which is set to #1 in BIOS boot order) is briefly accessed but almost immediately the message Disk read error. Press Ctrl + Alt + Del to reboot appears.

Did I miss a step, or what did I do wrong? Could the partition offset or cluster size be the reason?

Please note, I want to do the process manually and don't want to use tools like the HP USB format tool or anything like that, because they'll invariably place the partition at sector 63 which I'm trying to avoid for performance reasons.

Thanks in advance!

My System SpecsSystem Spec
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18 Oct 2011   #2

Microsoft Community Contributor Award Recipient

ME/XP/Vista/Win7
 
 

Try method two in this tutorial:
USB Windows 7 Installation Key Drive - Create
My System SpecsSystem Spec
18 Oct 2011   #3

Windows 7 Professional SP1 32-bit
 
 

Aha, maybe the bootsect command is overkill...I'll try the procedure again without it and see how it goes.

Thanks theog!
My System SpecsSystem Spec
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18 Oct 2011   #4

Windows 7 Professional SP1 32-bit
 
 

Problem solved!

The bootsect command was indeed redundant and not necessary, but that wasn't the real issue. It was the cluster size.

Apparently you can't boot from an NTFS primary partition formatted with clusters larger than 4K (the default). Once I did that, my USB stick booted perfectly (while still having the sector offset of 64).

This is a pretty straightforward issue but obviously it would very rarely be encountered - who installs Windows to an NTFS partition with large cluster sizes anyway
My System SpecsSystem Spec
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 Made bootable USB but getting "Disk read error" at boot time, why?





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