Are you using a 15khz screen?

Do you have an ArcadeVGA ? if not , how do you expect to run your windows in 15khz?

Because under Dos , it is easy with ARCMON.SYS , but under windows , if you don't have a ArcadeVGA, there is PowerStrip (but doesn't work with all card) or may be a video card with a TV out but the quality is not very good.