The simplest way to create a hot spot on a Windows computer is to use Virtual Router, download latest version from virtualrouter.codeplex.com.  If you have a LAN connection, simply add a Wifi adapter to your computer, you do not have to connect the Wifi adapter to an Access Point, you are going to make the Wifi adapter an Access point. 

If, on the other hand, you only have a Wifi adapter and you are already connected to an Access Point, you can still use Virtual Router to make your Wifi adapter a second Access Point, therefore allowing other Wifi devices to connect thru you.  ( this is handy when you are in hotel where they charge you for Wifi access per computer, all you have to do is connect to their Wifi on your laptop, and then using Virtual Router, you allow many other devices to connect thru.  The speed is excellent.

Another example for the use of this software is, let say you are at an airport, where they charge a wifi connection fee, you connect and pay for your laptop to go online, then by running Virtual Router, your other additional Wifi devices can go online for free.

VirtualRouter.CodePlex.com is the simplest program to use, It install and get up and running in less than 30 seconds.