Make sure to back up the db from start all programs data back up and restore
once the back up is complete go to drive:\programfiles\symantec\sepmanager\data\backup
move the db zip file to other location
Also move Server private key back up to another location as these are the certificates for clients
once you move above to another drive or location then remove sepm and reinstall it
After reinstall stop sep manager service and then
move above zip file to its original location by creating backup folder
and then re run data back up wizard to restore the db
once db is complete
re run the management server configuration wizard
please do not make any changes to server private key folder
attaching document for your reference
http://www.symantec.com/business/support/index?page=content&id=TECH160736&actp=search&viewlocale=en_US&searchid=1314736679298