here is one way of dual booting (written by me)
http://www.geekstogo.com/forum/Dual-booting-Linux-Windows-t254158.html
another way is allowing linux to partition your hard drive and installing linux to the free space,
this will erase the windows bootloader from the mbr and add grub (a linux bootloader) to your mbr, it should give you the option to boot linux or vista from the first boot screen,
the downside = if you don't like linux and remove it then you will have to remove grub from the mbr and replace it with the vista bootloader,
another way is to use a specific version of linux.
ubuntu linux can be installed in vista, it can be removed by add/remove programs,
yet another way is to create a bootable flash/pen/thumb drive with you distribution of choice,
this will not affect your vista in any way at all,
another way is use a virtual machine program, virtualbox is the one to use
http://www.virtualbox.org/
as it supports the linux file system, its very simple to use and free,
virtualbox is just a program that you install - then create a virtual disk (this is just a sort of file created on your existing hard drive),
then just install any distribution to the file through virtualbox,
this will not affect vista at all, as you are just installing a program,
the final way is just remove vista and install linux
linux is free and easy to use, it can do everything that windows can and much faster and safer,
command line learning is only if you want to, its not neccessary at all,
my daughter is 7 years old and she can use linux, yet she has no idea at all about command line and i have no need to do any command line work on her computer