I have a similar setup to yours, and when I upgraded to Windows 7 x64, as far as I can remember I downloaded only the x64 latest version from http://www.steinberg.net/en/support/downloads/halion_symphonic_orchestra.html and installed it, and then the latest eLicenser. Read the “What’s New …” notes regarding backward compatibility with HSO projects created in older versions first though!
The content (library) had already been installed on a seperate disk so it was just a matter if using the “locate content” function in the Options menu. I’d imagine you should be able to find the content on the original DVD and just manually copy that into a folder of your choice.
When you use the “locate” function, a file dialog will open and you can navigate to the folder to which you’ve copied the content, but I have found that it’s necessary to select all the files (“Ctrl-A”) as it doesn’t seem to be sufficient to just select one file in the content folder. I think it searchs all selected .HSB files for content.