qemu on linux doesn't boot for winxp install via usb

hi guys,
I try to install windows xp via qemu. I can only boot from usb and somehow it is my problem.
I run a Winxp/xubuntu10.04 Dualboot-system with some virtual drives in windows ( till letter f:? ).
at qemu I created an image from 30Gigabytes and entered this command from the imagefile's directory :

"sudo qemu-system-x86_64 -localtime -usbdevice -hda /dev/sdb -m 384 -boot d winxp.img"

the answer is :

"qemu-system-x86_64: -boot d: drive with bus=0, unit=0 (index=0) exists"

I had to set the usb-stick in the fstab file with this command :

"UUID=X	/media/usb	vfat	rw,users,noauto,umask=000	0	0"

anybody experienced the same problem?

I would appreciate any kind of help

greetz