Resize Operation Failed while resizing hard drive during unetbootin HD install

I purchased a new IBM Thinkpad X40 with Windows XP a few days ago. It's a very nice piece of hardware, but I didn't get the CD-ROM media slice. I thought it should be relatively easy to install from USB, but every method I've used (unetbootin, pendrivelinux, and the manual method from the Linux help documentation) has hung up during boot at initramfs, so I tried the unetbootin hard drive method.

It seems to boot in to the 8.04.1 live CD, but when it comes to the partition resize operation, I get the "resize operation failed" error. I've defragmented the Windows XP hard drive and disabled the XP hibernation feature. I tried to use the partition editor in the Ubuntu system menu, but it won't let me dismount the hard drive. Not surprising since it's running from the hard drive. But it that's the case, then how is the install supposed to work?