When you install multiple OSes many things can go wrong or produce
unintended consequences. What is supposed to happen is the the last
OS installed will detect previous OSes and provide the right
configuration for each. However, there is lots of room for error.

Excellent article!

For those wishing some more info on boot blocks, boot loaders, and
even booting more than 4 OSs, here's a short list of URLs from one
of my files:

http://en.wikipedia.org/wiki/Master_boot_record
http://www.ata-atapi.com/hiwtab.html
www.win.tue.nl/.../partition_types-1.html
www.cse.iitk.ac.in/.../MultibootOSInstallation.pdf
http://www.sun.com/blueprints/0905/819-2889.pdf
http://www.ranish.com/part/

Don't be put-off by the "sun.com" URL; the PDF document is entitled
"CONFIGURING MULTIBOOT ENVIRONMENTS ON SUN X64 SYSTEMS WITH AMD
OPTERON PROCESSORS" but the info is applicable to all OSs using grub
and its appendix describes a multiboot solution using the Ranish
partition manager to support more than four OSs (in case you're
attempting something "interesting" with your new 1TB disk :-)

Let's not overlook the grub docs (in many formats: text, PDF, HTML,
etc.):

http://www.gnu.org/software/grub/manual/

And this (GNU partition editor (gparted)) is an ISO of a minimal
Live CD with gparted which I've used to setup many a double or
triple boot system:

http://gparted.sourceforge.net/download.php