Can I run my CAD programs (which were written for windows) on Linux?
Possibly. There’s a Windows emulator for Linux called Wine. It runs a lot, even older games. If it runs in XP, it’ll likely run in Wine. If anything, create a new Parallels desktop, throw Ubuntu on there and see how it runs for you.
Can I run my CAD programs (which were written for windows) on Linux?No, but you can run Windows_mumble in a VirtualBox in Linux. This works very well, I am using it to run the Atmel Development environment under Windows7. It's pretty slick.