Hl-dt-st dvdram gsa-t20l has stopped working.

try this first,,follow the link verify operating system

http://h10025.www1.hp.com/ewfrf/wc/softwareDownloadIndex?softwareitem=ob-46803-1&lc=en&dlc=en&cc=us&lang=en&os=228&product=3224052

you may need to install updated firmware for the optical drive,but they are giving me any download options,you will have to start here,download the 4 troubleshooting programs and run them ,if they cant fix the problem,im guessing that a firmware download may appear,let me know what you find,verify operating system before downloading good luck
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c00828604&tmp_track_link=ot_recdoc/c00820047/en_us/c00828604/loc:4&lc=en&dlc=en&cc=us&product=3224052