Look harder or, actually, more carefully. ;-)
I'm sure you went here:
http://www.microsoft.com/
Probably then saw "Internet Explorer 8" under the popular downloads
in the right-side of the screen...
http://www.microsoft.com/windows/internet-explorer/?ocid=ie8_s_94735d11-65d1-4bb8-bf6f-72d7b059a928
On that page - if you looked in the lower left section, you should
have seen "Internet Explorer 7"...
http://www.microsoft.com/windows/internet-explorer/ie7/
(as well as "Internet Explorer 6", but that was not your question.
;-))
Once there - on the right side/centerish - you'll see a section
titled, "Get Internet Explorer 7" and a drop-down menu asking you
to select your operating system... And a "Go" button.
You've probably got it from there. ;-)
In case you don't, and I will assume you want the version for
Windows XP 32-bit...
http://www.microsoft.com/downloads/details.aspx?FamilyId=9AE91EBE-3385-447C-8A30-081805B2F90B
Hope that helps!
(BTW - if you mean you have been using Internet Explorer 8 -
Uninstall it to revert back to 6 before you attempt to install 7.)