Just few days back, Microsoft released Internet explorer 9 (IE 9) RC version. Even though IE 9 is not available for Windows XP or below, still its a big leap in terms of improvements for Microsoft browser i.e. Internet explorer. The reason behind the non -availability of Internet explorer IE 9 for Windows XP is debatable but in my opinion, this is a pure marketing decision.
Anyway, the installer available for Internet explorer from Microsoft is a web installer which means the installer downloads rest of necessary files while installing which often leads to problems while installing IE9 if your Internet connection fails in between.
If you need a full offline installer for IE 9 for Windows 7 to use on different computers, here are the links to download the full offline installer.
PS: Thanks Ashwin for the links.