Partition and Common folder

[mykle]

Hello, I have trouble with partitioning in linux since I was so
dependent on the partition manager provided in the installation of
ubuntu. What is really the parition if I want to install ubuntu feisty
on 20gb and the other is for slackware 12 still 20gb? Doing this would
be going to a manual installation.

Another is that will it be possible to have common folders, I mean
that all linux distro will refer to this folder/s say /home. I want
that my home folder can be accessible to both linux distro and
everytime I want to have a fresh installation the /home will not be
erased.

How I wish a have e extra pc at home so I can play around with linux
apart from my production pc. I might erase my windows partition where
most of my work resides hehe.