Invalid MS-DOS function trying to create Win 10 recovery from ISO

Question

Hi,

I downloaded the DELL Windows 10 ISO file and followed the instructions to create a bootable USB drive using "diskpart".

The bootable USB was created ok.

Then the instructions say to mount the ISO file and copy the contents of the mounted file to the USB drive.

When I try to do this, I get error messages "Invalid MS DOS function" which first occurs with the file "bootsect.exe.mui" and occurs with several other files if I choose "skip" as an option.

Does anyone have any ideas as to how this problem might be fixed?

So far I have tried this with 2 different USB drives from 2 different manufacturers - one 8 GIG and one 16 GIG and both produced the same "Invalid MS-DOS function" error.

Thanks!

For reference, the steps taken to create the bootable USB drive are as per the DELL documentation here:

www.dell.com/.../SLN299044

i.e.

1. Verify that the USB key can be erased and is at least 8GB.

2. Insert the USB key into an available USB port.

The Dell Hosted Recovery ISO should only be used on Dell systems. It is not designed or tested to be used with non-Dell PCs.

WARNING:These steps will erase all data from the USB key

Windows 8.1 and Windows 10
1. At the desktop, right-click the Startbutton and select Command Prompt (Admin)

5. Type diskpart and press Enter.
6. Type list volume and press Enter.
7. Determine the volume for the USB key, which should be marked Removable
8. Type select volume #, where # is the number obtained in the previous step.
9. Type clean and press Enter.
10. Type create partition primary and press Enter.
11. Type format fs=fat32 label='OS install' quick and press Enter.
12. Type active and press Enter.
13. Type exit and press Enter.

Then the instructions for copying the files from the ISO to the USB drive:

Copy data from the ISO image to the USB key
1. For Windows 8.1 or higher, right-click the ISO and select Mount
2. Copy the contents of the ISO to the USB key.

... and that is when the "Invalid MS-DOS function" error occurs.

Any help gratefully appreciated!

ieee488 · Answer

http://answers.microsoft.com/en-us/windows/forum/windows_10-files/ms-dos-invalid-function-after-upgrading-to-windows/ade061ec-dbfd-4225-bf05-b67d5485a08a

yetanotheruser · Answer

Thanks very much for the link.

I tried chkdsk /f on the mounted volume that I'm trying to copy - but it doesn't seem to work as the "disk" is write protected apparently.

D:\>chkdsk /f

The type of the file system is UDF.

Cannot lock current drive.

Windows cannot run disk checking on this volume because it is write protected.

... or should I run that on the C volume instead of the ISO volume?

maszynista · Answer

I'm having the same problem. Has anyone found a solution? TIA

Saltgrass · Answer

I don't know about the OP but what he was saying did not make much sense as far as Mounting an .iso file and copying the contents.

I normally create a bootable USB flash drive from within Windows where you can use Diskpart from an administrative command prompt, then mount the .iso and copy the contents to the flash drive.

I will go back and check the original directions to see if there is a problem with something that old.

I also use 8 GB flash drives since the size of a 64 bit image gets really close to 4 GB.

Windows General

Invalid MS-DOS function trying to create Win 10 recovery from ISO

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