This article was previously published under Q311385
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When you try to create an MS-DOS startup disk, you may receive the following error message:
An unexpected I/O error has occurred.
This issue can occur if you try to create an MS-DOS startup disk with an unformatted floppy disk. When Windows XP creates an MS-DOS startup disk, the Format utility tries to write to existing sectors on the floppy disk, and because an unformatted disk does not have a data structure, the Format utility generates the "An unexpected I/O error has occurred" error message.
To resolve this issue, format the floppy disk before you try to use it to create an MS-DOS startup disk.
To create an MS-DOS startup disk in Windows XP, insert a formatted floppy disk into the floppy disk drive, double-click My Computer, right-click your floppy disk drive, click Format, click Create an MS-DOS startup disk, and then click Start.