Five free Linux Operating Systems

1. Ubuntu
Ubuntu is a fast, easy to use and secure operating system. If you are already using windows you can run Ubuntu within your current operating system.
Current version requirements

• 500 mhz x86 processor
• 512 mb of system memory (RAM)
• 4 Gb of hard-drive space
• Graphics card and monitor capable of 800x600
• Either a Cd/Dvd-Drive or a Usb port (or both)
• Internet access is helpful

http://www.ubuntu.com/



2. Fedora
It's a completely free to use, stable and powerful operating system.
Current version requirements

• 400 MHz Pentium Pro or better processor (comparable AMD, Cyrix, and VIA processors also acceptable)
• At least 768 MB memory (RAM), 1 GB recommended for best performance
• 10 GB disk space / storage 
• http://fedoraproject.org/en/

3. openSUSE
openSUSE is  also a free and Linux-based operating system.
http://www.opensuse.org/en/

4. Debian
Another free operating system for your computer.
http://www.debian.org/

5. Linux Mint
http://www.linuxmint.com/