Use the HP Networking Upgrade tool to see if your current 3rd party Networking certifications allow you to go "to the head of the line" for an HP Networking certification. http://h17007.www1.hp.com/us/en/training/certifications/upgrade-path.aspx
Select the certification you are interested in. Then Select all of the certifications you hold that apply. Click on the "Show Upgrade Path" and you will be given a list of exams you need to complete.
For Storage, go to the ExpertOne Fast Track page to see what Upgrade paths your EMC and NetApp certifications give you. http://www.hp.com/certification/fast_track-storage.html. Scroll down to the "One Path to Two Certifications" section and click on the certification you are interested in. Scroll down to "Upgrade Paths Available" and click on the Upgrade path particular to the certification you currently hold.
This will open a new window into our Certification Explorer tool. Click on "Review and Complete Prerequisites" to review what is needed prior to achieving the certification and then click on "Complete Requirements".