If you don't install the official sound drivers for your card and use the generic windows drivers the volume levels will differ, this also happens on vista and win7. The official soundcard drivers usually have logaritmic volume levels while the generic windows have linear volume levels so at lower volume slider values level the generic drivers usually sound noticeably louder.
Thanks for the tip. I generally run a driverpacks offline installer so i guess i use whatever they choose. On my personal rigs, i guess i will go to my vendors website next install.