1) Download and extract the plugin
2) Copy the ajw_purgedata folder to your system/expressionengine/third_party folder
*** PLEASE ENSURE YOUR DATA IS BACKED UP ***
Add the following plugin call to a template:
This will delete all entries from channel with the id 9 which are more than 2 days old.
You can adjust the days= and hours= parameters to suit your needs.
There is an additional parameter:
which will cause the plugin to print out which entries would be deleted but will not actually