Cannot Burn CD's when I put in a new blank CD

hi

firstly you might want to create 2 separate questions here because you've got two different topics on two different machines - it may make it easier to more clearly track and categorize the question and answer for each. You can edit your original post and create a 2nd one with the other half of your double-question.

anyhow, I don't have an answer regarding your first question, but regarding your file sharing problem:

in order to directly connect those two Macs with an ethernet cable, you must use a special cable called an "Ethernet crossover cable", or be using an ethernet hub or switch in between the 2 machines.

If you are simply trying to connect them directly using a standard Ethernet cable like the one you'd use to connect to an Ethernet jack in the wall, it won't work. Newer Macs can be connected directly with an regular cable, but not certain older Macs, see this Apple support document.