Abyss Web Server X1 is a very compact Web server for Windows. There are two versions for the software: X1 and X2. The only real difference is that X1 is free and that X2 is paid (it also offers better support options). Functionality-wise, they are pretty much the same.
The installation takes less than a minute, and by the end of it, you have a running web server on your computer, which you can use to host your own websites. By default, Abyss is configured to start with your computer, so, as long as the PC is running, Abyss should be active as well.
You can access the configuration console by going to your computer's IP address on port 9999. From the console, you get access to all the settings. Abyss allows you to set bandwidth limits, both globally and per IP address. It comes preloaded with several MIME types, so that you can start adding objects to your website and use themes. You can modify them, though.
Security is a big issue when you are running a web server to the world. There is a security feature called Anti-Hacking protection. It can ban certain IPs when they send too many requests (flooding). You can specify the ban time and also filter out certain IP addresses (usually the ones you work from).