DLA = Drive Letter Access
Software that allows you to drag and drop files to a CD one at a time like you would with a hard drive. Normally in XP when you drag files to a CD you only "apparently" write them to disk immediately. The files actually hang around waiting to be written to disk together. DLA allows you to actually write them to disk immediately - one by one - using a disk format called UDF which I personally try to avoid because not all PCs are set up to read it.
I found some info that explains a lot here....
http://aumha.org/win5/a/xpcd.php