|Internet Explorer 6.0 installs MSXML 3.0 in replace mode. Here is the text from the Internet Explorer 6.0 Readme.txt file:
Internet Explorer 6 is shipping with msxml3.dll installed in override mode.
This means that all calls into any msxml DLL will be routed to msxml3.dll.
Please pay special attention to any XML, XSL, or data island issues that may occur.
On Windows XP(Home/Professional), Internet Explorer 6.0 installs MSXML 3.0 SP2 (8.20.8730.1), which can only
be installed in replace mode.
Other supporting links:
INFO: Version List of the Microsoft XML Parser (Q269238)
HOWTO: Determine the Version of MSXML Used by Internet Explorer (Q296647)