multiples partitions on external HD and usb boot

Hello everyone.

I’m trying to install opensuse 12.1x64 from my external USB hard drive.
This hard drive has 3 partition:
-A 976.56 GB XFS partition
-A 881.30 GB NTFS partition
And a 4.98 GB EXT4 partition

I tried using imagewriter as described here SDB:Live USB stick - openSUSE (this is what i used for live gnome usb).
The problem i found is that imagewriter doesnt let you use a partition of the disk but the whole 2TB space and i dont want this.

Any ideas? Thanks in advance