I was transitioning some machines to 64 bit Windows 7 and my old PC3 file wasn't working. I was thinking it was time to create a new PC3 with all the changes to the operating system, but when I went to add a plotter I could not find the Add-A-Plotter Wizard.
With a little digging I found this... addplwiz.exe. It was hiding deep in C:\program files\autocad land. Do a quick search on your PC to find yours if you ever end up loosing it like me.
By the way, I was right, the new PC3 file works like a charm.