Well, you wouldn't. But why not develop your first client using an open platform like HTML5 such that it works on every operating system whether proprietary, free, desktop or mobile? Deliberately limiting your userbase to just those using Windows seems to me like leaving money on the table.
Because you're already working on pre-existing software (the Grid Poker software) that is Windows-based, and while in the middle of this, dudes with guns from the Nevada Gaming Commission suddenly raid you, you flee the country, and want to get the site back up in a matter of days rather than months?