As you may be knowing, 64-bit editions of Windows include 32-bit Internet Explorer as well as a 64-bit version. This has been the case since Windows XP Professional x64 Edition and the reason that both editions are included is for compatibility with addons. When 64-bit IE was first introduced, most addons like Flash Player, Java, and most ActiveX controls were 32-bit only. 32-bit addons cannot work with 64-bit IE, that's why Microsoft bundled both x86 and x64 IE versions. Users could easily open whichever IE they wanted but this changed with Internet Explorer 10. Let us see how.
The first 64-bit version of IE was Internet Explorer 6, included in the 64-bit edition of Windows XP. From IE6 all the way till IE9, you could open 32-bit IE from C:\Program Files (x86)\Internet Explorer\IExplore.exe and 64-bit IE from C:\Program Files\Internet Explorer\IExplore.exe. In the Task Manager of 64-bit Windows, you can see which IE processes are 32-bit from the Processes tab.