The Apple support homepage is the main portal to help you answer all of your questions about your new Apple hardware and software products, featuring user forums, troubleshooting pages, and tutorials.
CentOS -- Community ENTerprise Operating System is a free rebuild of source packages freely available from a Prominent North American Enterprise Linux vendor.
The Microsoft Help and Support home page is your portal to help and support for Microsoft products. Download the latest updates and find top issues, error messages, and troubleshooting tips for Windows XP, Windows Vista, the 2007 Microsoft...
Debian GNU/Linux is a free distribution of the GNU/Linux operating system. It is maintained and updated through the work of many users who volunteer their time and effort.