I have a standard Apple US keyboard but I often have to type in German. I find the OS X shortcuts easy to remember and I am comfortable with them.
To type the umlauts you have to type option+u (u as in umlaut) followed by the letter that needs the diacritic.
When I use Windows in VirtualBox I have to fall back to the Windows combinations (e.g.AltGr+p for ö) which I find difficult to remember (I don't use VirtualBox a lot).
Is there a way to map the usual OS X key combinations to Windows?