You really inspired me for another attempt. After so many hours trying to get the install right.
Your thread made me try it again. And I finally got it back to work.
I'll explain in order to help someone with the same problem.
OS : Windows 8
First I wanna add that I use the original Halion Sonic discs for this ( boxed ) ( I've purchased HS2 as an update )
First you de-install all the HS installations on the computer.
Than you install the original Halion sonic ( version 1.0.0 ).
Then you download the 1.5 content update from the downloads area on http://www.steinberg.net
Then you download the HS2 update from HS1 from the downloads area.
Make sure that when you install these you tick the box " all users " otherwise it'll probally won't work.