Unwanted closing of DVD-RW burn in Win 7 with any software

adarryl

I store a lot of my digital imaging files to optical disk. I have gone away from CD's to DVD's to get larger capacity. Problem is, no matter what I do, my disks have being getting closed/finalized where I can no longer add files later no matter what burner software I use: Win 7's internal program that I believe is Roxio based and 2 freeware programs including Ashampoo and CDBurnerXP. What is going wrong and how can I fix it? It's very frustrating to save 500 MB's of digital images to a DVD-RW only to later find the disk appears in My Computer with "UDF" (universal disk format) over it with properties showing the disk as full thus making 4.2 GB no longer accessible. FWIW, I have used 2 different DVD-R's and 2 different DVD-RW disks (Sony and Ridata). It doesn't seem to make any difference. Out of nowhere, my disks are getting finalized without my authorization. Help!