Now, this should be a simple task, but I'm trying to make things difficult. Basically, I'm trying to install Ubuntu 7.10 on an external USB drive, so that it can be booted in both VMware and as a native boot. Within VMware, I'm using the entire physical disk, and set it to SCSI (0,1) and added another dummy IDE drive, to emulate my internal disk when natively booting.

Well, I'm able to install just fine from either location (VMware or CD) but I keep getting GRUB errors when trying to load in the opposite location (usually Error 17, also Error 18 once[boot partition too high in the drive, fixed]). Also seeing a lot of Error 5: Partition table invalid or corrupt

Can anyone help me achieve this?

Which GRUB stage fails?

And could you please explain the dummy IDE drive a bit more?

In the native boot, are you setting your USB drive bootable, or using GRUB on your internal disk to select it?

PS, do you make sure your USB drive is unmounted before trying to boot from it in VMWare?

ok, a bit of an update. I have it working now. I had to edit /boot/grub/menu.lst
the root line i changed from hd1,1 to hd0,1 and it boots fine in both locations now. I just have to copy over the correct xorg.conf now in order for the window manager to show correctly (and reconfigure VMware Tools)
the only difficulty i'm having now, is that when i'm running VMware as a non-privileged user, it says it can't find the virtual disk file (.vmdk) i browse for it, and it keeps saying the same thing. I think its a limitation of VMware itself now.