Wi-Fi lets us share the Internet and files among multiple computers. In your home or small office this is all made possible by your wireless router. However, you can also create a virtual wireless router on your computer, taking it anywhere you go, great for mobile or temporary uses.

Creating a virtual wireless router can extend the wireless Internet signal in your home or office to a computer that’s just outside the coverage of your main wireless router. Another use is that you can purchase Internet access for one computer at a hotel or Wi-Fi hotspot and share it with other people or devices. Plus you have a mobile wireless router in case you want to share files with other people or devices, in the car, at a café, in a meeting, anywhere.

If you are non technical Webster Consulting recomends using Connectify and heres how you do it.

Create a Wireless Hosted Network in Windows 7 with Connectify

Start by downloading it from Download.com. Once you open it, you can use the wizard to configure the network name, password, and Internet sharing. Then after you hit the Start button, other computers and devices can connect. You’ll see a list of currently and past connected clients on the Connectify window.
Create an Ad-Hoc Wireless Network with Any Windows (or other OS)

If you can’t use a Windows 7 computer to host the virtual Wi-Fi router, you can create an ad-hoc (or computer-to-computer) wireless network. This will appear slightly different than a typical wireless network to other devices but works on all Windows versions and operating systems and is supported on all wireless adapters.

If you want to share the Internet among all the computers, someone must connect via an Ethernet cable to a router or port for the Internet. Or if someone has two wireless adapters they could connect to the Internet source on one and then connect to the ad-hoc network on the other. To share the Internet they could use the Internet Connection Sharing (ICS) feature of Windows, Open the Network Connections window, right-click the network adapter that’s connected to the Internet and select Properties. Then select the Sharing tab, check the Allow other network users to connect through this computer’s Internet connection, choose the network connection name of the Microsoft Virtual WiFi Miniport Adapter from the drop-down box, and click OK.

Start by creating a network profile for the ad-hoc network and connecting to it on that same computer, which starts broadcasting it. Then others nearby should see it on their list of available wireless networks. Once they connect, they’ll receive an automatic IP address.
Remember to be secure

When you create a Wireless Hosted Network in Windows 7, with Connectify, the use of WPA2 encryption is required. People can only connect to your virtual wireless network if they know the encryption key/password. However, people that connect may be able to view and/or edit your files if you have file sharing enabled. If you don’t trust the other people, ensure you disable file sharing using the Network and Sharing Center.

If you create an ad-hoc wireless network, remember to use encryption if you want to control who connects. You’ll probably be limited to using WEP, which requires a 5 or 13 characters. Keep in mind, this encryption is hackable so use carefully. Once people connect, the same thing applies as discussed above; disable file sharing if you don’t want them to access your shares.