[racket] Newbie question - Drscheme hangs on directory-exists?

Hello -

If I enter "(directory-exists? "C:\iconsource")" into DrRacket
I would expect it to answer with "#t" or "'#f" but in fact the
cursor goes to the next line, leaving an indent.
I am running this on Windows 7.

As a newbie I do not understand this behaviour.

Is there a tutorial on file i/o with all the complications
of persuading DrRacket to find data input files etc?

Regards

_John Sampson_