I think you can just quote the paths with spaces, e.g. instead of
You can also move the Nyquist directory to a new place or uninstall it and
reinstall it elsewhere. If you move it manually, you should (carefully)
change the XLISPPATH variable in the registry to match. The XLISPPATH
variable is described in the manual -- see "installation" in the index, or
look for "Win32 Installation" in the Introduction and Overview.