Gun laggy on widescreen

I'm playing Gun on a 19" wide screen monitor and I'm getting really bad stuttering in it, which doesn't happen when i play it on my old 15" monitor. The game doesn't have a native wide screen resolutions but I've read that you can edit the registry to get wide screen resolutions but all it does is stretch the image so i want to avoid doing that. Anybody experienced this and got any solutions?

Thanks