Question : SQLServer 2005

What is the difference between IA64-ENG,X64-ENG,X86 and how can I see which one I am running or installed.

Answer : SQLServer 2005

IA64 is a 64-bit version targetted specifically at servers running on Intel Itanium processors.
x64 is the 64-bit version for Zeon, Pentium and AMD processors
x86 is the standard 32-bit version