We tested our WPF application on Windows XP in VMware Player (with VMware Tools) and noticed that there were errors in the drop-down lists : all options will appear when you click on the ComboBox, but when you hover over them they disappear .
Then we noticed that Visual Studio Express 2010 has exactly the same problem with its menu.
Here the menu item hangs itself in the middle of the screen:

Here the menu item is stretched :

We have installed WMware Tools:

VMware. - , VMware, XP, WPF WPF 4.0?