Internet Explorer 10 contains both 32 and 64 bit versions,
The default, when started, runs the 64 bit version as the base and each tab runs the 32 bit version to allow most add-ins to run.
If you want to run the 64 bit version in all the tabs you must go to tools (Gear in tool bar), internet options
and under the advanced tab, down by Security, check Enable Enhanced Protected Mode.
To go back to 32 bit, you must uncheck this option.