in proteus you can make device ... (menu Library/Make device)
you need to create device (pin, pin names, body) then you need to assign packaging info, name it and that's about it. You can also attach dll with application that will simulate the working of the new device, but in order to make that dll you have to contact proteus guy's and ask for SDK. (not sure it will be easy task to program the pic24FJ simulator tho)
I don't know. I use Zeus Pro. You can go to their website and download their library of components via altera quartus v. 8.0. i usuaully click on the add on dialog box to the right.
You can also download Loki Plus from Ti's website. They have a lisrt of their chip sets available un the TI Tina link. Its similar to pspice and/or multisim.
That or IBM's Anubis Circuit simulator package. Intel uses Manticore simplex.
In OrCAD you make the component symbol in Capture (the libraries- make your own or add to an existing one). Then you make the footprint in Layout. There is a field in the library (Capture) that you type down the footprint you want used. It's name should be the same as the name of the footprint in Layout and it will link them for you when you generate the ratnest as when you move a design from Capture to Layout.