There are specific distros (distributions) out there, each one with a different download link.
I see you're probably new to Linux, so I recommend Linux Mint. This distro is based off of Ubuntu, but I strongly recommend you to download the one based on Debian (a much more solid base):
I like the Cinnamon Desktop better than MATE, so:
For 32-bit Mint Cinnamon: http://www.linuxmint.com/edition.php?id=101
For 64-bit Mint Cinnamon: http://www.linuxmint.com/edition.php?id=102