[racket] [Racket] Finding files

Can Racket be made to detect the PATH environment variable in Windows 7?
If not, is there a way of emulating it so that one does not have to 
write out
the complete path of any file mentioned in Racket code? This includes data
files the program might be writing to or reading from.

Also, I am looking at the document 'Systems Programming with Racket'. It has
instructions for making a file "serve.rkt", which I have done, but 
Racket cannot
find it, even if I specify the complete path. I have tried to understand 
the documentation
on folders and files, but I am not succeeding.

Regards

John Sampson