I just installed the Windows Driver Kit for XP - Windows 7 and this may come as a silly question, but what is the difference between a "free build" and a "checked build"?
PS: I'm not a driver developer, I installed it merely to check some header files for P/Invoke.
Driver developers will often run their code on "checked" Windows builds - Windows editions that have been compiled without optimizations and are, as such, easier to debug crashes on and will product better memory dumps and have more accurately matching symbols.
The "free" builds are the normal releases.