[plt-scheme] How to update MzScheme from v352 to v4.1?

With MzScheme v352 and DrScheme, version 4.1, english, installed on
Windows XP Professional, Service Pack 2, I would like to upgrade
MzScheme to v4.1 so that I can use it at the command line and in
Emacs.

However, according to "Download MzScheme v4.1" (see
http://download.plt-scheme.org/mzscheme/mz-4-1-bin-i386-win32-exe.html),
>Note: If you have a previously installed version of MzScheme,
uninstall it before using this installer. 

Unfortunately, it is not quite clear how to do this.  MzScheme is not
listed in the Add/Remove Programs control panel applet, and there is
no Uninstall.exe or similar file in the MzScheme folder.  Also, the
included documents do not describe specifically how to uninstall it.

What should I do to upgrade from MzScheme v352 to v4.1?

Also, in trying to figure out how to uninstall MzScheme v352, I opened
the "Setup PLT.exe" file in the MzScheme directory.  Does this mean
that I now need to uninstall and reinstall DrScheme, version 4.1,
english?  I tried it out, and it seems to continue to work fine.

Thanks in advance for any assistance.

-- Benjamin L. Russell