one posibility is the agent has been upgraded from 2.0 to 2.1 hence the reason the Reg key is not there.
Tom Howarth
VMware Communities User Moderator
Tom Howarth VCP / VCAP / vExpert
VMware Communities User Moderator
Blog: http://www.planetvm.net
Contributing author on VMware vSphere and Virtual Infrastructure Security: Securing ESX and the Virtual Environment
Contributing author on VCP VMware Certified Professional on VSphere 4 Study Guide: Exam VCP-410