multiple partitions for single Ubuntu install

[Rubicon421]

I've read about several people setting up ubuntu with multiple partitions for a single install, so they can use one for root, one for home, user, etc...

What is the advantage to this setup?
If I do it, how many partitions should I make? Should I create them with Windows before I begin installing ubuntu?

[Pumalite]

With Vista; allocate space for Ubuntu first:
http://www.howtogeek.com/howto/windows-vista/working-around-windows-vistas-shrink-volume-inadequacy-problems/
With XP; you can use the Live CD; go 'Manual':
10 to 20 GB for '/'
The rest minus 1.5 of your RAM for /home
1.5 of your RAM for /swap

[Partyboi2]

The advantage of having /home on its own partition is that if you ever need to reinstall Ubuntu at any time everything eg videos, personal data etc on your /home parition will not be touched.
To setup a /home partition you can choose manual when it comes to the partitioning stage of the install and create a ext3 partition with the mount point set to /home