Depending on the storage speed this may take a few hours, but this is less what would be concerned about because you can do this with the VM powered on. What I am concerned about is that the Exchange shows 6 snapshots in the Snapshot Manager and 6 snapshots for one of the virtual disks, but 7 snapshots for the other virtual disk. This basically means you should run "Delete All" to get rid of the snapshots. However, DO NOT run Delete all if your hosts are not already on ESXi 4.0 Update 2 (or later). With earlier versions you could run out of disk space with using "Delete All".
In any case, ensure backup is disabled while you delete the snapshots to make sure it does not try to create a new snapshot while deletion is in progress!
André