There is nothing wrong with using Offline Vault in EV 2007, if there is a problem updating these two particular client machines, the best course is to troubleshoot the issue, not just upgrade... so I would totally disagree with the SE on that point.
If you want to retrieve all items from their archive, then you can right click the archives node in the VAC, do an Export Archive. You have some choices to make after that, such as exporting it to PST, or back to the original mailbox. That's up to you, and the two clients, how they want their data.
To exclude them from further archiving, you can disable archiving for them. There is a toolbar button to disable a user from archiving.
Hope that helps,
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