Quick glance about difference between various IIS Versions

The following table summarizes the important differences between versions of IIS. IIS 4.0 IIS 5.0 IIS 5.1 IIS 6.0 Platform Windows NT 4.0 Windows 2000 Windows XP Professional Windows Server 2003 family Architecture 32-bit 32-bit 32-bit and 64-bit 32-bit and 64-bit Application process model TCP/IP kernel MTX.exe TCP/IP kernel DLLhost.exe (multiple DLL hosts in medium- or high-application isolation) TCP/IP kernel DLLhost.exe (multiple DLL hosts in medium- or high-application isolation) HTTP.sys kernel When IIS is running in IIS 5.0 isolation mode: Inetinfo.exe (for in-process applications) orDLLhost.exe (for out-of-process applications) When IIS is running in Worker Process Isolation Mode: W3wp.exe (multiple worker processes) Metabase configuration Binary Binary Binary XML Security Windows authentication SSL Windows authentication SSL Kerberos Windows authentication SSL Kerberos Security wizard Windows authentication SSL Kerberos Security wizard Passport support Remote administration HTMLA HTMLA No HTMLA Terminal Services Remote Administration Tool (HTML) Terminal Services Cluster support In Windows NT 4.0 IIS clustering Windows support Windows support WWW services IIS on Windows NT 4.0 Personal Web Manager on Windows 9x IIS on Windows 2000 IIS optionally on Windows XP Professional IIS on a member of the Windows Server 2003 family   For more detailed information refer the following link http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/7b037954-441d-4037-a111-94df7880c319.mspx?mfr=true