Symptoms
Is there a way to delete process instances.
Diagnoses
Client had a lot of test processes that were cluttering up workspace.
Resolution
You can do this by deleting the Versions of the process under Workpsace > Mangement Console > Workflow Server > Processes > Versions?
http://help.k2.com/onlinehelp/k2blackpearl/userguide/4.6.8/webframe.html_reference-ws_mcon-workflow-processes_versions_process_deletion.html