[racket] [Racket] Making Racket find files

On Feb 1 I wrote:

"I have not been able to find a succinct description how to cope with 
the Windows directory system to make Racket find user-created files, 
either to run them as programs or open them as data sources or 
destinations. Perhaps there is a particular directory where they have to 
be for Racket to find them, and this can be set as a default in some way 
(environment variable or whatever)."

So can Racket be made to read environment variables such as "path" in 
Windows 7? Or does one have to write out the whole path
of a file? If so - forward slashes or backslashes? How many times do 
they have to be escaped?

Regards

John Sampson