OK - I've now got an answer from a different forum, so here it is for anyone else:
Windows 2003 doesn't have any built in software for recording - you have to install Roxio or Nero or similar. If you look in My Computer, the drive appears as a CD read only drive, and if you put a blank recordable disc in and click on it , it says " F:\ is not accessible" just as if there were no disc in the drive. However, if you start from the Roxio menu, the disc is detected correctly and a recording can be made. I've no idea why it doesn't behave like XP does, but that's how it is.