[plt-scheme] How to load xml.ss?

xml.ss exists in
    "C:\cygwin\home\metaperl\install\PLT\PLT\collects\xml\xml.ss"

not
    "C:\cygwin\home\metaperl\install\PLT\PLT\collects\mzlib\xml.ss"

but I don't know what to do to get DrScheme to find it.

Also, I tried to load xml.ss via "Add Teachpack" but then I was told:

The teachpack file 
C:\cygwin\home\metaperl\install\PLT\PLT\collects\xml\xml.ss did not load 
properly.
teachpack: export of pi from 
"C:\\cygwin\\home\\metaperl\\install\\PLT\\PLT\\collects\\xml\\xml.ss" 
conflicts with already existing definitions

Transcript below:


Welcome to DrScheme, version 206.
Language: Pretty Big (includes MrEd and Advanced).
 > require
require: bad syntax in: require
 > lib
. reference to undefined identifier: lib
 > (require (lib "xml.ss"))
open-input-file: cannot open input file: 
"C:\cygwin\home\metaperl\install\PLT\PLT\collects\mzlib\xml.ss" (The 
system cannot find the file specified.; errno=2)
 > require-library
. reference to undefined identifier: require-library
 > require