We had a bug in our application that only manifested on Windows 8 and later.
The problem was that we were passing NULL instead of some other sentinel value (MSDN said to use a specific sentinel value). XP/Vista/7 took NULL anyway and the effect was the same as the sentinel value but in Windows 8 it did something different.
Do they still do it?
But last time I checked the .NET Framework abused some Win32 API calls [1] so if you had some WinForms application you'd end up with loads of errors in code that wasn't yours.
Might be fixed, it's been a while since I looked.
[1] http://connect.microsoft.com/VisualStudio/feedback/details/3...
Now I wouldn't be able to tell you what are the incriminated part of Windows.
There's even an app that is written in dotnet and that is not Win 7 compatible. Can you believe it ???