I'm having exactly the same problem. I bought my 330Ci last week also knowing that the passenger window would only go down about 4 inches. Last night i took it all apart only to find that i couldn't get access to these 2 bolts holding the window as the cable was all chewed up in the regulator.
The only bolts I could see which were attached to the window looked like they were star shaped and not your typical bolt. As I had no tool that could remove this (if I could get the window down that far) I'm now left with my door card in the boot (trunk). I'm seriously tempted to just take it to a garage to fix, as the half an hour repair guide took me 2 at least!