Oh i forget one thing.
If you don't want to risk on your pc system.
You can install without having a create 2nd space in your HDD.
Jolicloud has http://www.jolicloud.com/download
like 690mb download but it will not touch single file on your HDD.
and you can remove it if you don't like it.
Ubuntu is also great os.http://www.ubuntu.com/download/ubuntu/windows-installer
software called wubi is help you to have 2nd os in your HDD.
This software also can be remove without trouble.
Try it and if you really like it then~ try to install on your 2nd hard drive space.
PS. these are virtual space OS, therefore it will slower then install on 2nd hard drive.
But these days PC spec it won't hurt.