Here's a link that should do it...
http://ubuntuforums.org/showthread.php?t=24113
Post #5 is the method I've used. A very good 'save-yer-butt' CD you can dl and burn is PartedMagic. It has an easy GUI, boots to ram (about 50M), online access to google stuff and you'll have root access to your hard disks.