An alternative if you want to keep GPT partitioning (e.g. for disks greater than 2TB), but your bios requires MBR: hybrid mbr/gpt disk
There are several ways to create a hybrid mbr/gpt disk. One such way is to boot into a linux live CD that has the "gdisk" utility. At the command prompt become root with "su -" or "sudo -i" depending on the linux distro, then use gdisk to modify the partition table. This writeup is from memory but should be accurate. worked for me. Follow the prompts in gdisk if it differs from here.
Hope this helps someone!
su - [become root]
gdisk /dev/sda [replace "sda" with the correct drive]
x [enter expert mode]
r [enter recovery / translation mode]
h [create hybrid partition table]
1 5 6 8 [select the correct partitions]
[enter] [keep the current partition type]
n [not bootable]
[enter] [keep the current partition type]
y [set this one bootable! gpt5, mbr2]
[enter] [keep the current partition type]
n [not bootable]
[enter] [keep the current partition type]
n [not bootable]
w [write changes to disk]
y [confirm]
q [quit]