Microsoft will soon be releasing IE8 as a critical update via Windows Update. If you want to control this situation and decide on when you want to download and install it, go to this link and download the IE8 auto download blocking toolkit.
http://www.microsoft.com/downloads/d...displaylang=en

When you run the EXE, it extracts the contents to a folder of your choice. Then open a command prompt in the folder you extracted the blocker tools to and type
IE80Blocker.cmd /B
and then hit enter.

This creates a registry key at
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Setup\8.0
with a key value name of
DoNotAllowIE80
and a dword of
1

If you later decide to allow the auto download and installation, just change the dword to
0

Note that the blocking action will only prevent IE8 from downloading automatically. If and when you decide to download and install IE8 manually, this registry entry has no effect on that.