Native SharePoint 2010 Backup

I am using following script to remove old backups. For some reason it unable to remove an old backup entry. I see an entry when I go to Central Administration  --> Backup and Restore History. The entry is from Dec.2012.

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# Location of spbrtoc.xml
$spbrtoc = "\\Servername\SharePointBKP\spbrtoc.xml"

# Days of backup that will be remaining after backup cleanup.
$days = 7

# 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 harddisc."

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