Exchange 2010 -DeleteContent doesn’t free-up space on a drive

I'd spin up an instance of an older version of Windows, install the Exchange 2003 management tools, and continue with the decommissioning procedure just to be safe. I'm assuming this is a production environment, and I don't think I'd toy around with deleting records via ADSIEdit.

Move public folder data to Exchange 2010

Public folders are an optional feature in Exchange 2010. If all client computers in your organization are running Microsoft Office Outlook 2007 or later, then public folders are an optional feature. However, if Outlook 2003 clients are in use, then public folders are required. In addition, if you're currently using public folders for collecting, organizing, or sharing documents and other information and you want to continue doing so, you can use public folder replication to move your public folder data to Exchange 2010.

Learn more at: Understanding Public Folder Replication 28

How do I do this?

You can use the Exchange Management Console to perform this task.

1. In the Console tree, click Toolbox.
2. In the Result pane, double-click Public Folder Management Console. The Public Folder Management Console appears.
3. In the public folder tree, click or expand Default Public Folders, and then select the parent public folder of the public folder that you want to move to Exchange 2010. Note: To configure replication for the offline address book (OAB) or for Schedule+ free/ busy information, expand System Public Folders, and then click OFFLINE ADDRESS BOOK or SCHEDULE+ FREE BUSY.
4. In the Result pane, right-click the public folder you want to replicate to Exchange 2010 and select Properties.
5. On the Replication tab, click Add to select an Exchange 2010 public folder database and then click OK.
6. By default, Exchange uses the replication schedule configured for the public folder database. To create a custom replication schedule for the public folder, clear the Use public folder database replication schedule check box and select one of the settings in the list.
7. To create a customized schedule, click Customize.
8. To set the schedule, click the time grid in the Schedule dialog box. Public folder replication will run during the time slots that you specify.
9. Click OK to close the Schedule dialog box.
10. To specify the age limit for items in this public folder, type the number of days in the Local replica age limit (days) box. Items that have reached the age limit are deleted.

Note: Age limits should be used for public folders only. They should not be used for System Folders, such as OFFLINE ADDRESS BOOK or SCHEDULE+ FREE BUSY.

11. Click OK to close the Properties dialog and to save your changes.
12. Repeat Steps 4-11 for each public folder you want to move to Exchange 2010.

How do I know this worked?

You can use the Get-PublicFolder cmdlet in the Exchange Management Shell to verify replicas on the Exchange 2010 public folder database. For example, to determine the replicas for all public folders in the public folder tree, run the following command: Get-PublicFolder -Recurse | Format-List Name,Replicas To determine the replicas for all system folders, run the following command: Get-PublicFolder \NON_IPM_SUBTREE | Format-List Name,Replicas 29 Learn more about the cmdlet at: Get-PublicFolder

Visit Link : http://technet.microsoft.com/en-us/exdeploy2010/default.aspx#DeploymentCheckList/ee958313/2007