My girlfriend wants to install openSUSE 11.0 on her usb HDD. She already has ubuntu 8.04 as her main O.S. I have tried to install but always came up against the problem that the partitioner sees the ubuntu \ partition and doesn’t allow me to create another \ partition on the USB drive. Is there someway around this?? 
What are you using to install? Are you saying that the installation partitioner does not see the external disk at all? And how do you want the booting to be set up?
I am using the SUSE 11.0 live dvd installation which I got from the magazine Linux Format September 2008. I have installed several discos in the past on USB drives with no problems. However because this install program sees a root() partition on my internal hard disk it will not allow me to create another ()partition on the usb drive. I suppose I could make an image of the internal () partition, delete it and then install SUSE on the usb drive and then restore the image partition to my internal drive, but I would rather find a more elegant solution.
The installation partitioner makes a “suggestion” based on what it finds, but it is only a suggestion. At this step, click on Create Partition Setup and then Custom Partitioning. A screen is shown with all your existing disks and partitions. The only mount point shown will be for your Ubuntu swap partition. If the partition(s) you want to install to have already been created, click on Edit to specify the mount point, and if you wish, you can also specify you want the partition formatted. If you need to create new partitions, click on Create; specify the mount point (one will be suggested, but you can input whichever you want), the file system to be formatted, and the size (don’t input anything in the Start field, and in the End field, input the size in gigabytes, that is unless this is the last partition taking the remaining space, in which case you don’t need to enter the size).
You can then see the results of your setup in the partition table screen. Verify this is what you want, click Next, and you return to the installation partition step and will see a summary of what the installer is going to do. Re-verify.
Important note: You also need to decide how you want the booting to be set up. If Ubuntu and grub are already on the internal drive, it will be easiest the control the boot from Ubuntu. But this won’t be the default openSUSE setup. So you will need to instruct the openSUSE installer how you want the set up. Post back your preference here and I’ll give you what to do at the Booting installation step (it’s very easy).
Thanks for your input. I had been creating my own partitions as you had suggested. The problem in the end was mine. I assumed unwisely that I had to manually create another (/) partition for SUSE on the USB drive. The installer takes care of that. I now have success.
Glad to have been of help 