I don't see that as a recommendation to uninstall IE7 before installing
WinXP SP3. However, if you think you'll ever need to uninstall IE7, yes, it
would be advisable to uninstall it before installing WinXP SP3:
<QP>
If you are currently running IE7 on XPSP2, Windows Update will offer you
XPSP3 as a high priority update. If you choose to install XPSP3, Internet
Explorer 7 will remain on your system after the install is complete. Your
preferences will be retained. However, you will no longer be able to
uninstall IE7. If you go to Control Panel->Add/Remove Programs, the Remove
option will be grayed out.
This behavior is by design and here is why. When we install IE7 on Windows
XP SP2, we backup the existing IE6 files in an uninstall directory. Those
IE6 files are the ones that shipped on XPSP2 plus all the security updates
you've installed while using IE6. Windows XP SP3 contains a newer version of
the Internet Explorer 6 files. If you have XPSP3 on your system and
uninstall IE7, your system would revert to the backed up (older) version of
the IE6 files rather than the newer XPSP3 version. You would end up in a
mixed file state in Windows where most files would be the upgraded XPSP3,
except for the IE6 files restored when uninstalling IE7. This state is not
supported and is very bug prone. To ensure a reliable user experience, we
prevent this broken state by disabling the ability to uninstall Internet
Explorer 7.
If you must uninstall IE7 after you have upgraded to XPSP3, then you have to
first uninstall XPSP3, and then uninstall IE7. After this series of
uninstalls, you will be reverted back to a XPSP2, and a stable version of
IE6, so feel free to upgrade to XPSP3 again.
If you install IE7 after you install XPSP3, then you will be able to
uninstall IE7 at any point and be reverted to the newer IE6 version that
ships in XPSP3. The restriction on uninstalling only applies to when you
install a Windows Service Pack release on top of a standalone IE release.
Keeping this in mind, you might want to uninstall IE7, upgrade to XPSP3 and
then install IE7 again so you can uninstall IE7 in the future if need be.
</QP>
Source:
http://blogs.msdn.com/ie/archive/2008/05/05/ie-and-xpsp3.aspx
This is the usual practice for MS: If IE6 is installed in, e.g., Win2K SP4
and it was installed prior to installing SP4, you must uninstall SP4 before
you'll be able to uninstall IE6.