Images for creating an ubuntu system are available at:

       http://www.ubuntu.com/download/desktop

I suggest you use the 64 bit version if your hardware supports it.
Don't be confused by the "intel" vs. "amd" terminology. For historical reasons
the 32 bit version is refered to as "intel", and the 64 bit version as "amd".
The amd version works on any intel/amd cpu that supports 64 bit code.

You want the latest Long Term Support release: Trusty Tahr aka. 14.04 LTS.
Documents on this site have only been tested with 14.04 LTS.

Instructions for the installation are available from:

	     https://help.ubuntu.com/14.04

You can play with ubuntu by booting from the DVD without actually 
installing it on your hard disk.  I STRONGLY suggest you obtain a 2nd
physical hard disk for the installation.  Too many things can go
wrong trying to resize your existing windows system to allow
installation of ubuntu on the same disk.

You can choose to install with your primary windows disk connected,
in which case the grub installer will be installed such that you can choose
between windows and ubuntu during boot.  You do need to be very careful
to install on the 2nd disk, and to pick the 2nd disk for the grub loader.

The safer alternative is to do the install with the windows disk unconnected.
The disadvantage of this is that grub won't be aware of the windows disk after you
re-attach it, requiring you to break into the BIOS during boot to select ubuntu.

With my 1st system I installed with the grub loader, and it works well,
except that if I physically disconnect the windows (ie. 1st) disk. it
stalls during the expected ubuntu boot.  Any insight here would be greatly
appreciated!