Ok I finally got everything running again, however the first DVD I tried to burn was "Halted with errors" and the DVD drive disappeared from the system again (ie. no longer listed in device manager).
I decided to firstly replace the cable, and then maybe remove my CD-ROM drive which is on the same EIDE cable, then if necessary replace the drive (from EIDE to SATA),so I went in to a local computer shop to buy the cable and was given some really strange advice.
(1) Devices dissapearing from the system is a common problem which is caused by the device driver, it can only be solved by wiping the HD and reinstalling windows. (surely I could just install an updated driver? answer: No)
(2) The "Halt with write errors" are occurring because there are two CD/DVD drives on the same EIDE channel, ie. data blocks are being sent to the wrong drive because they're both sharing the same cable. (I've never had a problem with this type of setup before)
(3) Another option would be to replace the (EIDE) DVD writer with a new (SATA) DVD writer, where it would have it's own cable connecting it directly to the MB. (at today's prices, I'm considering this)