Directory Opus 9 and above have native x64 versions which fully support 64-bit Windows.
The following FAQ is retained for Opus 8 users:
[quote]Directory Opus 8 is not supported on 64-bit versions of Windows.
You can install the 32-bit version of Opus 8 on a 64-bit version of Windows but you should be aware that certain features may not work or may need to be disabled to avoid conflicts with system folders such as Control Panel.
Explorer Replacement is the main thing in Opus 8 which is known to cause problems on 64-bit Windows. We recommend that you turn Explorer Replacement off.
Aside from the Explorer Replacement feature, Opus 8 itself should generally work fine.
Keep in mind, though, that as a 32-bit process you will see virtual versions of System32 and similar directories due to the way Win64 runs 32-bit processes (and the way it stores 64-bit binaries in the real System32).
System-wide hotkeys created by Opus 8 may only work when other 32-bit processes are active.[/quote]