Dual Boot Vista-Ubuntu


I had install Vista in my computer. Now, I want to try to install ubuntu 8.04LTS in my computer. I tried several times but each times I try, I say that the installation failed. It say that something related to GRUB. I try follow the procedure describe here but I'm a bit not understand.
can you describe on how to do it?
thank you
Hi shadowanz, welcome to NST.

You're going to need to give us more info about that "something about GRUB" error - the exact wording would be great.

Most likely you didn't install GRUB to the right device when selecting the "Advanced" button. Be sure to use a valid /dev/sd* notation instead of (hdx,y) and that it refers to the same drive & partition that was shown in the partition manager when you selected the root "/" partition for Ubuntu to be installed to.
thanks computer guru

well, I tried to install it just now

the error say

unable to install GRUB in (hdo)

Executing 'grub-install (hd0)' failed
this is a fatal error
I see...
Can you explain to me about the step 6? Because I'm not quite understand about it.
In my case the device should be like this

[device] [type] [mount point]
[/dev/sda1] ntfs
[/dev/sda5] ntfs
[/dev/sda6] ntfs
[/dev/sda7] ext3 /
[/dev/sda8] swap

so, how should I configure step 6?
I tried it just now
unfortunately same situation happens

Is there's a possibility the error comes from the iso CDor the DVD drive ?or there's another method to make dual boot vista-ubuntu?