You can either delete or retire it.
Either manually, or automatically using the wanted purge settings at:
- Settings -> Notification Server -> Purging Maintenance - Purging Maintenance
If you delete it, all data is gone ... there is no undelete.
More about retiring computers:
http://www.symantec.com/business/support/index?page=content&id=HOWTO52993&actp=search&viewlocale=en_US&searchid=1352964487814