The FlexWindow Arch component makes creating arched windows much easier and faster - Scale the window, or specify it's width and height in the Options Window, and the arch is automatically calculated.
In addition to the usual settings for specifying frame dimensions and adding glass divisions, you can control the number of segments the arch is made of.
With 2 segments you'll get a very pointy window. More segments will make the arch increasingly smoother, but watch out! Too many segments will make the dynamic component heavier and the overall performance slower. On an average workstation this isn't too noticeable but on 'aged' computers you will feel the slow down.