You have to install things manually, not using the autoinstaller.
This is simple.
Also you can't install Wodpress and your forums in the same directory.
Well you could but it will be a huge mess.
Basically makes your wordpress site go to www.domain.com
and then forums to point www.domain.com/forums
I have little time today, you can try to get a hold of me on IRC and I might be able to help out.