With older legacy programs. If a program doesn't work in Windows 7 or 8 you can right-click the executable and choose "run in compatibility mode". It will run that way by default next time so you only need to do it once. That works for most programs but not everything.

I have a customer that's a large medical office and they have an application that only runs on XP, not even Win 7. That's causing HIPAA compliance security concerns and they're trying to move off of it, but when you have a lot of data in a legacy application it's not simple. We also support hedge funds, equity management firms and engineering/construction firms. So far the CAD programs run OK on win 7 but not all on win 8.