A user calls to report a problem. she is trying to install an application on a windows 7 system, but cannot. in the past, she installed applications on her windows xp system without any issues. she has always been a member of the power users group. what do you suspect is causing the installation issue?

Compatibility is the answer. Sometimes software was only designed to work with Windows up until a certain version was released. When Windows 7 was released it has a feature called Windows XP mode. Where software than ran on Windows XP would run on Windows 7 without any problems. This is called Backwards Compatibility.