"For good" is difficult...
It's just moisture that doesn't dry out - from condensation etc. - ventilation helps - you need to scrub with antifungal wash - let it dry and scrub again. A dehumidifier will help to dry the walls and leaving a window slightly open all the time too.
http://www.scotland.gov.uk/Publications/2005/05/10103020/30217
http://www.diydata.com/problem/condensation/condensation.php
http://healthandenergy.com/mold_prevention.htm
Good luck...
Peccavi
February 2010