Usually, I use Macs. At work though, I have to use Windows 7.
I still use an Apple mouse and I am used to being able to scroll both vertically and horizontally.
In some programs such as Google Chrome, this works just as expected. The window with focus scrolls vertically and horizontally. Some other programs such as Microsoft Office or Photoshop will only scroll vertically. Yet some other programs like Visual Studio (2010) will send vertical scroll events to the currently active "frame" and horizontal scroll events to whatever other frame they feel like.
Is this due to the mouse doing something wrong or are Windows programs just not able to deal with horizontal scroll events correctly?