I first started with Vista install, then install Ubuntu, pretty much with default settings. Then I discovered I couldn't boot Vista.
Fixed by using Vista recovery CD. Go to Command Prompt and type
bootrec /fixboot
bootrec /fixmbr
(more details at AusCoder)
Then use Ubuntu CD to boot up and install grub. Then boot back to Vista, and get EasyBCD. Add linux partition. I need to use the grubless option (check -Grub isn't installed- option) to finally get it to work.
These are the guides that were helpful to me:
A key point is to not overwrite boot-loader thing of Vista when installing Ubuntu. So make sure to put the grub to the Ubuntu partition.