Can't access http:// pages using MSIE, other browsers work fine

Hello,

I use WinXP Pro SP2 and my default browser is Firefox. Sometimes I'd like to
view some pages using MSIE, but I can't access http:// pages - https:// ones,
as well as local html files, work OK. This means I can't access Windows
Update and keep my Windows as secure as possible. Other browsers (Firefox,
Opera) are OK, they can access http:// pages, but they cna't be used on
Windows Update site - this site requires MSIE. I tried to repair my WinXP
install from the CD, but it didn't help.

Can you help me, please?

Tomas Valusek