For Dell OpenManage support you will need to install Dell OpenManage (yeah - really :)) (minimum 5.1) onto the device you want to monitor. Ensure that net-snmp is using srvadmin, you should see something similar to:
Download OpenManage from Dell's support page [Link](http://www.dell.com/support/contents/us/en/04/article/product-support/self-support-knowledgebase/enterprise-resource-center/systemsmanagement/OMSA) and install OpenManage on your windows server. Make sure you have SNMP setup and running on your windows server.