MOVB-17 Got to love this one

Stop error message when you start a Windows Vista-based computer: "0xC1F5"

(Knowledge base article 946084, accessed on March 20th, 2008)

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WORKAROUND

If you have only one disk installed, and if you have access to Windows XP or Windows 2000 installation media, restart the computer by using the Windows XP or Windows 2000 installation media. Next, format the offending disk, and then reinstall Windows Vista.
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Hu ho, looks pretty bad :)