hello jeff,
You can:
Browse the datastore where this VM resides
Select the VMDK required and select download to local drive
Once saved, you can create a new VM, and attach this drive.
If you want to test a virtual machine that is similar to the original one, you can simply clone it.
If you export to OVF you can deploy N number of VMs from the OVF template
However, to export the VM to OVF you will have to power down the VM.
Suhas