With Outlook 2010 you can clean up the PST file manually.
as i use a german outlook, i only got the german vocables.
"Datei" -> "Kontoeinstellungen" -> "Kontoeinstellungen..." -> "Datendateien" ->
click on the archive file -> "Einstellungen" -> "Jetzt komprimieren"
maybe someone talking german and using a english outlook can help you further.
translation:
"File" -> "Account Settings" -> "Data Files" -> click on the archive file -> "Settings" -> "now compress"
