Hi,
Windows can be used as embedded OS, but none of it's version is real time (time determinist). So if you need to design a real time appliction, you will need something like VxWorks, QNX or other kernerls like these ones.
There is an other alternative, RTX from Venturecom / Ardence. This one can add real time functionalities to windows OS :
h**p://www.vci.com/products/windows_embedded/rtx.asp
h**p://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnxpembed/html/hardrealtime.asp
Replace * by t