You cannot downgrade the IE version on Windows 8.0/8.1.
Windows 8.0 ships with IE10. To upgrade to IE11, you must upgrade to Windows 8.1.
Windows 8.1 ships with IE11. To downgrade to IE10, you must reinstall Windows 8.0.
Windows7, ships with IE8, and can be upgraded and downgraded between IE8 <-> IE11.
Note that IE versions less than IE11, become unsupported in January 2016.
Don
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