Drive Letter Access (DLA) is a discontinued commercial packet writing application for the Microsoft Windows operating system that allows optical disc data storage devices to be used in a manner similar to floppy disks. DLA is a packet writing technology for CD and DVD media that uses the UDF file system. DLA is not compatible with Windows Vista and newer, although a patch exists to fix this issue under Windows Vista. Roxio Burn was introduced on April 30, 2009. As a replacement for DLA, it remedies compatibility issues Internet Explorer 8. History DLA was originally developed by VERITAS Software and later sold to Sonic Solutions in 2002. It was common as it was shipped with a majority of CD and DVD recording drives, where DLA came as a custom OEM version for the branded drive. Also, most PC systems from Dell, HP, IBM, Sony and Toshiba came with DLA pre-installed. An OEM version was often available for download for the specific computer system. With Windows Vista support for DLA was either dropped or it was replaced by a similar product, like Drag-to-Disc. Technology To use an optical medium such as a CD-R, CD-RW, DVD±R or DVD±RW just like a floppy drive it is necessary to utilize a technique called packet writing. After formatting the optical media it is then possible to write data in small packets, hence the name “packet writing.” The optical drive unit has to support the ability to write in small units, which all modern CD and DVD recording drives do. This way it is possible to save files onto optical media, as well as change, rename or delete them, or copy files separately onto the media. Without packet writing, optical media like the above-mentioned would have to be written on in one big block, like Disc At Once (DAO), Session At Once (SAO) and Track At Once (TAO), because these media types normally do not support sectors. After formatting with packet writing the medium is sectored in blocks that can be written to individually. The preferred file system is the Universal Disk Format (UDF) in versions from 1.50 onward, which is also used by DLA. Packet writing is not required for writing DVD-RAM. DVD-RAM media are already sectored (which can be seen when looking at the surface of an empty DVD-RAM disc) and the hardware logic of DVD-RAM capable drives supports sectored read/write operations as required