take out old
hd, put in new
hd, put in
dvd, turn on system, follow instructions on screen
but first as a matter of urgency get any files you want from the old
hd - at the very least remove it from the system as it could die at any time, and while it's runnign it may be (its likely to be) trashign more of your files on a continous basis - and when it does thats it - kaput - unless you want to spend several hundred on data recovery that is