Thinking out aloud - Dave Hunter's SharePoint Blog

# Clean-up (old) backup files created by WSS v3 (STSADM.EXE)
# Created by Marco
# Tested with PowerShell RTM v1.0

# Location of spbrtoc.xml
$spbrtoc = "\\server\backup\Sharepoint\spbrtoc.xml"

# Days of backup that will be remaining after backup cleanup.
$days = 14

# Import the Sharepoint backup report xml file
[xml]$sp = gc $spbrtoc

# Find the old backups in spbrtoc.xml
$old = $sp.SPBackupRestoreHistory.SPHistoryObject | ? { $_.SPStartTime -lt ((get-date).adddays(-$days)) }
if ($old -eq $Null) { write-host "No reports of backups older than $days days found in spbrtoc.xml.`nspbrtoc.xml isn't changed and no files are removed.`n" ; break}

# Delete the old backups from the Sharepoint backup report xml file
$old | % { $sp.SPBackupRestoreHistory.RemoveChild($_) }

# Delete the physical folders in which the old backups were located
$old | % { Remove-Item $_.SPBackupDirectory -Recurse }

# Save the new Sharepoint backup report xml file
$sp.Save($spbrtoc)
Write-host "Backup(s) entries older than $days days are removed from spbrtoc.xml and harddisk."

• Create a batch file on the SharePoint 2007 server with the following commands:
  

STSADM –o backup –directory \\server\backup -backupmethod full -quiet
powershell.exe c:\scripts\SPFullFarmBackup.ps1

• Save the file and add a scheduled job for the batch file.

• Queries the spbrtoc.xml file and finds all the backups.
• Deletes older backups (by the value of days specified in the script – in this case 14 days).
• Deletes the associated backup files from the UNC path and save the updated spbrtoc.xml.
  

Thanks for Marco for the backup script http://blog.wauwwie.nl/Lists/Categories/Category.aspx?Name=MOSS%202007%20%2F%20WSS%20v.3