just got sound on one speaker O.o

hi guys out there,

i just downloaded your ultramixer 2 (2.3.5) demo, because im looking for a good dj program for beginning mixing and for partys.

so far everything was just great (yeah just wile downloading), but after installing and little playing around with this software i noticed that just the left front speaker and the subwoofer worked O.o

the only thing i did was putting my headset as monitors and “preview speakers”. but why is there just sound on the left front speaker?

my system is (this time, i`ll get new parts in 2 weeks):
asus p5ne-sli
pentium 4 550
onboard sound

and logitech z5500 connected via coax

need help!

I’m sorry my english isn’t the best -.-

thx, eck

edit: OS is vista ultimate 32bit

sry everything is ok now, it was my fault, the songs i played were just mono -.-