http://bugs.winehq.org/show_bug.cgi?id=22766
--- Comment #5 from Stefan Dösinger stefandoesinger@gmx.at 2010-05-19 17:17:41 --- I think you've got a point here
The dxdllreg service is only registered when installing the dx runtime with winver=win2k, which also installs old libs like directplay and directmusic which already ship with Windows XP. However, as far as I know there wasn't a AMD64 build of Windows 2000. So that means I'm running the installer in a mode it wasn't intended for.
When using winver = winxp(Installs newer stuff like XAudio, xinput, ...) there is no dxdllreg service registered. I also cannot find this service on my 64 bit Windows 7 box.
(Note that apparently you have to run the installer with winver=win2k once before installing it in XP mode, otherwise it complains about missing registry keys - most likely keys from the DirectX Windows XP ships with)
I guess we can close this as invalid then.