Which commands can be used via the command line to unzip a file?
Preferably something built into Windows or open source/free tools.
You could use :
http://membrane.com/synapse/library/pkunzip.html
or
7zip: http://www.7-zip.org/download.html
Free byte zip: http://www.freebyte.com/fbzip/
or infozip: http://infozip.sourceforge.net/