For those of you who, like myself, like online bookmark site Spurl, and could not get the Explorer Bar to show on Widndows Vista 64-bit, here is a simple way to do so:

1. Check which Internet Explorer you are running. I did so by looking at Windows Task Manager and looking for ieuser.exe and iexplore.exe processes. In my case, they had “*32″ marks next to it to indicate that it is 32-bit processes:
2. Open a 32-bit RegEdit by typing “c:\windows\SysWOW64\regedit.exe
3. In that editor, navigate to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Discardable\PostSetup\Component Categories:
   
4. Delete keys named {00021493-0000-0000-C000-000000000046} and {00021494-0000-0000-C000-000000000046}

This will force IE to rebuild its cache of Explorer Bars to load and, in my case, made Spurl show up nicely as a sidebar in IE.