From what you've written I'm guessing that you don't have the 32-bit version on your machine. A word to the wise:
http://www.zdnet.com/blog/networking/installing-32-bit-ie-9-on-64-bit-windows/802
Download the 64-bit version, as the 32-bit version will refuse to install. According to the article, that way you'll get the 32-bit version too.
That's just Microsoft for you...
Edit:
Just found this:
http://answers.microsoft.com/en-us/ie/forum/ie9-windows_7/internet-explorer-9-wont-display-some-websites/8f4e6cad-3c4f-e011-8dfc-68b599b31bf5
"There is a bug that causes massive display issues in IE9 if you have Helvetica installed. It will cause display problems on sites that declare Helvetica as the first font (in their CSS)."
and
"Yep, uninstalling Helvetica got rid of the problem with IE9! Additionally, I noticed that it seems to be only an Adobe Type 1 font that causes this problem. "
"I now have an OpenType format Helvetica font and it works just fine with IE9."