if your computer skills are not advanced I would recommending finding a local geek to do it for you. One factor may be that your old disk is dead which means you can't get information off of it cheaply if at all. second, newer computers have a different disk connections (SATA instead of IDE). Think of it like different plugs types that are not compatible.
Note to all members. I recommend that you backup you PCs. I personally use a tool called Mozy that only costs $5/month and automatically backs up your data every day. if you don't have that much data (< 2GB) then it is free. http://www.mozy.com
Please note I don't work for Mozy or get a finders fee