There is an option to "rescue" an installation by loading the DVD and going through the install process until just before selecting "install". Or you may find it useful to download and try Super Grub Disc http://www.supergrubdisk.org/
(always a useful tool to have).
Self-righteousness is a loud din raised to drown the voice of guilt within us - Eric Hoffer
Don't believe what it says on the right - I am anything but sagely; More oniony!