Code 39 error: why has my CD/DVD drive stopped working? I have a two year old Advent laptop, running Windows 7, which until recently has performed faultlessly. The problem I have now is that the DVD drive suddenly stopped working. When I click on the drive in Windows Explorer it says that Windows cannot load the driver and mentions "Code 39." Following earlier advice in your column I tried a cleaning disc and managed to work out how to uninstall and update the driver from Device Manager but it still refuses to work. Any ideas? Angela Hewlett, by email Well done for eliminating the two commonest causes of CD/DVD problems, however the Code 39 error message points to a fairly specific, and surprisingly common Registry glitch but it is easily rectified. The Windows Registry is a vast collection of System files, responsible for configuring a PC's hardware and software, so please don't try this if you are a complete novice, nervous, or very unlucky with computers. First create a System Restore point (Start > Accessories > System Tools > System Restore) then go to Search or Run on the Start menu and type "regedit." This opens the Registry Editor, navigate to the following Registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E965-E325-11CE-BFC1-08002BE10318}. In the right hand pane look for entries labelled UpperFilters and LowerFilters, plus any with .bak extensions. Right click on each one in turn and click Delete. Close Regedit, reboot and hopefully the DVD drive will be working once again, though you may find that some programs that use the drive may have to be reinstalled.