Create Task Scheduler Backup sharepoint Wss 3.0

One way to create a Task Scheduler on sharepoint Wss 3.0 is create a bat file and use the "Microsoft Scheduled Tasks" there you select the bat file and select the days or days that the service run, easy and fast...

"start"->"control Panel"->"Scheduled Tasks"->add task

create .bat file and associate the time
path C:\Program Files\common files\Microsoft shared\web server extensions\12\bin\
Stsadm.exe" -o backup -directory \\server\share -backupmethod full -overwrite

Microsoft have create a diferent scrip that delete older files a litle more complex but can be the way you want

How to automate the deletion of backups in SharePoint Server 2007 and in Windows SharePoint Services 3.0 by using a Visual Basic script

You can also manually delete backups. However, manually deleting backups does not clean the manifest file (Spbrtoc.xml) correctly.

the page i was base on http://www.iopus.com/guides/winscheduler.htm

Clean up backup files (Windows SharePoint Services 3.0)

http://technet.microsoft.com/en-us/library/cc967308.aspx