I need to create a site that interact with some windows applications. Currently this is done through direct calls so I would like these to run on the webserver. This means that the site will have to run on a Windows based system.
I have been doing some ruby lately and am very keen on using rails for the site, but have at the same time seen plenty of discouraging posts regarding this.
Should I rather use ASP.NET (MVC) for a windows system or is rails stable enough to handle this?
Ruby on Rails on Windows is not ideal, but it does work, and works just fine for most purposes. The biggest issue you will likely run into is that the community of people running RoR on Windows is very small, so the issues you do run into which are specific to RoR+Windows may be harder to get help on.
If leveraging existing community is very important to you and/or your project, then I do recommend going with ASP.NET MVC. The community there is much larger and easier to connect with than RoR+Windows, which is fairly niche. Although it's difficult to put an objective value on the added benefit of having a community of support, it's clearly one of the biggest selling points for any platform - the RoR community in general, for example, is a huge part of its continuing success.
I would add to Rex's answer that RoR+Windows is fine for development, but i would not use that as a production setup. In my case i do a lot of work in Flash/Flex/Photoshop while working on the backend at the same time, and of course running those graphics heavy apps on Linux is not very ideal, but the server i deploy to is Linux which is the only part that really matters.