Hi
There are queues which are safe to be purged (because they will just fill up again), and there are queues which should not be purged.
Generally, you should not purge them unless adviced to do so.
If you want to know what the queues do, fire up your EV Management Console, and click the "Help" button.
Then search for "MSMQ queue summary", which will provide you with insight on what they do.
Cheers
Michel