Vista - how can i use rear line-in port for rear speaker on Intel D945GCPE motherboard

I have Intel D945GCPE motherboard (integrated sound card) running Vista Ultimate x32.
It has two front and three rear audio ports.
I want to use Creative 4.1 speakers but cant figure out the right audio driver.

i've run XP on same pc with 6 channel audio....using line-in blue jack and mic-in pink jack as line-out....but i lost that realtek driver and the one i have with my intel disc doesn't allow me to do so....
the old realtek driver gave 6 channel option on XP....however I haven't used that driver on Vista n dont know if it works the same way....

the driver on my intel disc lets me chose 4 channel max....but hav to use headphone jack as front and line out as rear speakers....
on Vista I can switch to 4 channel but cant plug in rear speaker coz only one of front or rear jack works at a time....or both give same output....

my pc was configured by sm1 else previously so i cant say if he did smthing with bios or something else....

if sm1 kows a sol. please let me know...
i've been looking for it from a long time...