Thanks for your answer AlucardZero!
Debian Version: 5.0.8
This is what happens when try to install mysql-server-5.1 (translation aside)
Los siguientes paquetes tienen dependencias incumplidas: (These packages has dependency unaccomplished)
mysql-server-5.1: Depende (depends on
: mysql-client-5.1 (>= 5.1.49-3~bpo50+1) pero no va a instalarse
Depende: libmysqlclient16 (>= 5.1.21-1) pero no va a instalarse
PreDepende: mysql-common (>= 5.1.49-3~bpo50+1) pero 5.0.51a-24+lenny5 va a ser instalado
E: Paquetes rotos (broken packages)