my hard disk setting is like this:

one PATA IDE 300G with Windows XP, Vista and MBR installed.
one SATA2 IDE 250G with also Windows XP, Vista and MBR installed.
(I am doing this because my old PATA disk have some problem and I am migrating to new SATA2 disk)
one SATA2 IDE 250G for personal folder
one USB 80G for back-up

since I have 2 MBR, I can select which MBR to boot from my BIOS menu.

But I have a problem now when I am installing Mint 3.0 because ubiquity alwayse crashes when installing grub after installing everything else.

I try to fix it following ubuntuguide.org instruction using Super Grub Disk, it simply not able to find the linux partition.

then I tried to boot from live CD, when I enter grub and type "find /boot/grub/stage2" it returns "file not found" but I do find my linux partition in my first SATA2 IDE disk with ext3 file system using file browser and the file "/boot/grub/stage2" is inside.

so anyone can help me boot up my linux?

From the linux live CD post the output of

sudo fdisk-l