I just installed Visual Studio 2005 on my home PC (don't worry, it's a legal, fully licensed copy). It installed a version of SQL server that it calls SQLexpress; however, there is also a CD that came as part of the package called SQL Server Developer Edition 2005.

If I want to install that version of SQL server on my PC, it's asking me to pick whether I have a Itanium based operating system, X64 based operating system, or X86 based operating system. How do I find out which one of those I have? All I know is that I have Windows XP Pro.