[racket] simple question

Hi there, just cutting my teeth into programming (last time I did this was  
Pascal and Assembly with an old 6502 processor).

Here's my simple question: I am trying to create an executable file of the  
fahrenheit to celsius program (in version 2 of htdp), and getting the  
following error message:


call-with-input-file: cannot open input file: "c:\program files  
(x86)\racket\collects\unstable\private\expand.rkt" (The system cannot find  
the file specified.; errno=2)

=== context ===
C:\Program Files  
(x86)\Racket\collects\racket\contract\private\arrow.rkt:1445:3
C:\Program Files (x86)\Racket\collects\compiler\embed-unit.rkt:366:4:  
get-code
C:\Program Files (x86)\Racket\collects\racket\private\map.rkt:45:11:  
for-each
C:\Program Files (x86)\Racket\collects\compiler\embed-unit.rkt:366:4:  
get-code
C:\Program Files (x86)\Racket\collects\racket\private\map.rkt:45:11:  
for-each
C:\Program Files (x86)\Racket\collects\compiler\embed-unit.rkt:366:4:  
get-code
C:\Program Files (x86)\Racket\collects\racket\private\map.rkt:45:11:  
for-each
C:\Program Files (x86)\Racket\collects\compiler\embed-unit.rkt:366:4:  
get-code
C:\Program Files (x86)\Racket\collects\racket\private\map.rkt:61:17: loop
C:\Program Files (x86)\Racket\collects\compiler\embed-unit.rkt:366:4:  
get-code
C:\Program Files (x86)\Racket\collects\racket\private\map.rkt:45:11:  
for-each
C:\Program Files (x86)\Racket\collects\compiler\embed-unit.rkt:366:4:  
get-code
C:\Program Files (x86)\Racket\collects\racket\private\map.rkt:45:11:  
for-each
C:\Program Files (x86)\Racket\collects\compiler\embed-unit.rkt:366:4:  
get-code
C:\Program Files (x86)\Racket\collects\racket\private\map.rkt:45:11:  
for-each
C:\Program Files (x86)\Racket\collects\compiler\embed-unit.rkt:366:4:  
get-code
...


I checked my file directory, c:\program files  
(x86)\racket\collects\unstable\private\expand.rkt

exists!

Anyone ever have this problem, thank you in advance,

dt
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