After testing Windows 7 RC, I'm ready to remove it, but I want to use it's partition for multibooting different Ubuntu releases.

This is my current scheme:

/dev/sda1 ext3 /home/lovinglinux/videos
/dev/sda2 ntfs

/dev/sdb1 linux-swap
/dev/sdb2 ext4 /
/dev/sdb3 ext4 /home

Since I already have 3 primary partitions, I will format sda2 as an extended partition and create 3 primary ext3 partitions inside it. Then I will install a different Ubuntu version on each, using the same linux-swap from sdb1, but I don't want to share the home partition between each installation. So I need to know how do I mount them.

I'm assuming I will have to select the manual partitioning method. Can I have multiple partitions mounted as root or they will conflict with each other? Since I already have a separate partition for /home, will it be automatically mounted on every new version I install (I don't want this)? How exactly do I mount the same swap for all of them?