Default to MyISAM instead of InnoDB in Drupal 7
The quickest and dirtiest way to get all Drupal data into MyISAM perform the following:

Make a backup of /var/lib/mysql before doing these steps

step 1. mysqldump all data out of mysql

step 2. remove all folders and files from /var/lib/mysql, but leave the /var/lib/mysql/mysql alone because it contains user grants.

step 3. add this line in /etc/my.cnf

[mysqld]
skip-innodb


step 4. service mysql restart

step 5. reload mysqldump file back into data into mysql database

UPDATE 2011-10-04 04:28 EDT

step 1. Set Default Storage Engine to MyISAM

add this line in /etc/my.cnf 

[mysqld]
default-storage-engine = MyISAM


step 2. service mysql restart

Give it a Try !!!