An upgrade disk cannot be used to install XP onto a blank hard drive. The installer looks for a qualifying product and if it does not find one, halts with an error message.
Here are the possible upgrade paths
You do not say if the upgrade disk is XP Home or XP Pro, so I show both
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Installed OS upgrade to XP Home? upgrade to XP Pro?
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Windows 98/98SE Yes Yes
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Windows Me Yes Yes
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Windows NT 3.51 No No
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Windows NT 4.0 No Yes
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Windows 2000 Professional No Yes
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Windows XP Home N/A Yes
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