Some time back Microsoft's Internet Explorer team had released a FAQ for Internet Explorer Beta. You may want to check it out!

One bit of information I would like to reproduce here:

When Microsoft releases Internet Explorer 9, will it require Windows 7 Service Pack 1?

No!

Internet Explorer 9 will install on systems that have either Windows 7 RTM or Windows 7 with Service Pack 1 (SP1) installed.

When you install Internet Explorer 9 on a system that has Windows 7 RTM installed, additional operating system components are included as part of the installation of Internet Explorer 9.

When you install Internet Explorer 9 on a system that has Windows 7 SP1 installed, these additional components are already present with Windows 7 SP1, and do not need to be reinstalled when you install Internet Explorer 9. For this reason, a system reboot is not required when you install Internet Explorer 9 on a system that has Windows 7 SP1 installed.

Internet Explorer 9 is faster to install than Internet Explorer 8 because of an upgrade process that requires fewer decisions and less overall time.