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AutoCAD LT 2004 cannot be used to purchase the upgrade to Autodesk AutoCAD LT 2014, as only the latest 6 previous versions (from 2008 to 2013) are upgradeable to the 2014 version. In you case, you should buy a new license of Autodesk AutoCAD LT 2014.
If you purchase your 2014 version along with a 1-year Subscription, you'll be entitled to the Use of Previous Versions benefit. This means that you'll be able to download and install AutoCAD LT 2011. To find more about the Subscription Program and its benefits, please visit this page.