Downloading and installing Sitecore CMS

I m trying to download trial version to learn site core but i failed every time .....

Solution which i found

• Sitecore Express, which is for non-comercial use:
  http://xpress.sitecore.net/
• EDIT: You will have to contact Sitecore for a copy: http://www.sitecore.net/Company/Contact (thanks Yan Skylarenko)
  • There's lots of info for installing Sitecore on the SDN, as well as plenty of tutorials, cookbooks and references. Installation guides:http://sdn.sitecore.net/Products/Sitecore%20V5/Sitecore%20CMS%206/Installation.aspx
  • Sitecore fundamentals: http://sdn.sitecore.net/Developer/Training%20Materials/Fundamentals.aspx
  • Building a basic site: http://sdn.sitecore.net/Developer/Training%20Materials/Basic%20Site.aspx 
  Once you got permission you can download Site Core
• https://sdn.sitecore.net/Products/Sitecore%20V5.aspx
• https://sdn.sitecore.net/Products/Sitecore%20V5/Sitecore%20CMS%206/Update.aspx