When dealing with IDE, cabling and jumpering is very important. A single IDE port can support two drives, when using the proper cable and if the drives are properly jumpered - one for master and one for slave. That's where Larry's problem comes in - his DVD burner keeps insisting on being master and his hard drive is slave. This might be a failure of the DVD burner, it may want to be the only thing on the IDE chain. It probably was expected to be connected through SATA, but Leo says he could also look in BIOS to make sure there's no setting he missed there.
Next he was having issues installing software, and he believed it was because his drive was labeled "D". Leo says the way Windows typically works is it goes down the chain and starts with letter C, which the DVD burner would be. Larry says it isn't naming the DVD burner C, however. Windows could be labeling the drive "D" because it's a slave on the IDE chain.
Larry figured at this point instead of trying to find out why Windows was naming his hard drive "D", he would try to change its name in registry edit. Leo doesn't think that's a good idea though at all. The last thing he wants to do is try to trick Windows in registry edit.
Instead of messing with registry edit, he should just right-click on "My Computer", select "manage" and try to reassign it there. It wouldn't let him do this though because it's the boot drive. He could try a SATA adapter for his IDE drive. Go into the chatroom, there are a lot of suggestions there.