Please provide the details of what Exchange version and service pack level you are working with. Also, are you trying to delete these folders from a specific mailbox? These are the default folders and cannot be deleted. So please provide more details of the version and purpose you are trying to acheive. Thanks.
Try setting a <a href=”http://support.microsoft.com/kb/822938″>retention policy</a>. You can set it so that all mail in the deleted items is permanently deleted after whatever time frame you feel is appropriate. For our organization the deleted items folder automatically deletes all mail older than 3 months. All our other folders automatically delete mail after 15 months. Be sure and notify users of the change before implementation or you will get a plethora of calls requesting restores when people notice the mail is gone.
Also, you may need to do offline database defragmentation using <a href=”http://support.microsoft.com/kb/192185″>eseutil</a> on a regular basis. The nightly maintenance does not remove white space from the databases. The offline defrags will reclaim space for you and reduce the size of your databases.