I am adding a tip.Hope it would be helpful.
When we want to run a task (like sending emails or deleting the list items etc. . . ) in Daily basis or in Hourly basis then we can use a Timer job to this task .To see the timer job you can move to the Central Administrations then click on the operations tab, then in the Global Configuration section you can see the Timer job status and timer job definition. In timer job definition you can get the details of the timer job i.e. the title , the web application to which it is attached and the schedule type i.e. Daily, Weekly or hourly basis. To get the status of the timer job go to the timer job status, here you can view status.
Posted Oct 11, 2010, 11:35 PM
Creating Custom Timer Jobs in Windows SharePoint Services 3.0
Creating, Deploying, and Debugging Custom Timer Jobs in Windows SharePoint Services 3.0
Creating and Working with SharePoint Timer Job Definitions
Custom TimerJob in Sharepoint
Eran HeferPosted Oct 11, 2010, 2:02 PM
Check out this post - complete example of creating & deploying a SharePoint 2007 timer job.
http://ajaxme.blogspot.com/2010/10/how-to-create-deploy-sharepoint-2007.html
Eran Hefer.