Downgrade from MySQL 5

If you want a quick and dirty way and you don't have any databases, then you could do the following if you're using an rpm based linux:

rpm -qa | grep -i mysql-

Then use rpm -e on each match for MySQL v5.

Then remove /var/lib/mysql:

rm -Rfv /var/lib/mysql

Then edit /var/cpanel/cpanel.config and set:

mysql-version=4.1

Make sure that the skip file isn't there:

rm -fv /etc/mysqlupdisable

Then install MySQL:

/scripts/mysqlup --force

Then update the perl module:

/scripts/perlinstaller --force Bundle::DBD::mysql

Then recompile apache/php.

Of course, if you do have MySQL d/b's then you'll have to consult further on whether they can be downgraded and miss out the removal of the mysql dir.

Once done:

/scripts/upcp --force