Ubuntu Desktop GNU/Linux 14.04.2 Trusty Tahr LTS x64 Long term support version of the famous free and open source OS. 64bit version.

Update 14.04.2 – 2015.02.19

System requirements:

• x64 capable CPU
• 700+ MHz processor
• 512+ MiB RAM
• 5+ GB of hard drive space
• VGA capable of 1024x768+ screen resolution (from my experience, worked also on 1024x600)
• Either a CD/DVD drive or a USB port for the installer media
• (Internet access is helpful)

Installation guide:

• Burn the ISO to DVD or use the Pendrive Linux program to create a startup flash drive (Startup Disk Creator - if you use Ubuntu).
• In the BIOS settings of your PC, select DVD drive / USB flash drive (respectively) as your First Boot Device.
• Follow the instructions of Ubuntu installer.
• When the PC restarts during installation - log on to BIOS (DEL key, or F2 or other button), and select your Hard Drive as the First Boot Device.
• The installation will continue and you will log on to your Ubuntu desktop.

Notes:

• Ubuntu LTS version will be supported for 5 years (until April 2019).
• Even though you can see the name 'amd64', the OS will work on any x86_64 CPU, both Intel or AMD.

Enjoy!