While other solutions exist, the easiest way to run Windows on your System76 Machine is by using the program called VirtualBox. VirtualBox is a virtual machine
There are two versions of VirtualBox available. One is open source, but lacks support for USB devices. The other is proprietary, but also free (as in beer) and has USB support.
If You Don't Need USB Support
Some people don't need support for USB Devices, and others simply want only open source software. Either way, this method is easier to install, and thus recommended if you do not require support for USB Devices such as flash drives and MP3 Players.
For Ubuntu 9.10 and later, click on Applications > Ubuntu Software Center. In Software Center's search box, type in VirtualBox. Next double-click on the "VirtualBox OSE" entry and click on install. Wait for the installation to finish, then skip to the section titled Install Windows in VirtualBox below.
If You Do Need USB Support
This installation method is slightly more complicated than the one above, but it works equally well, and includes USB support.
Open a web browser and go to the VirtualBox Download Page. Select the the Ubuntu Package for your appropriate Ubuntu Version (9.10, 9.04, etc) and Architechture (i386, or 32-bit; and AMD64, or 64-bit). and download it. Allow Firefox to open it with "Ubuntu Software Center" (Selected by default) and click OK. Once the package has downloaded, the installer will automatically open. Click Install to proceed with the installation.
Install Windows in VirtualBox
Once it is installed, VirtualBox will be listed in your Applications menu under System Tools. Open it, then click "New". Run through the wizard. Now, click "Settings", then storage, then click the CD Icon. In the right-hand pane, under "CD/DVD device" select the the entry beginning with "Host Device". Check the Passthrough box, then click "OK". Now, insert a Windows Installation Disk and click start. Run through the installation normally.
Running Windows in VirtualBox
To run windows, simply open VirtualBox, select your windows virtual machine, and click Start. Note that once you open a machine and click in it, it will capture all keyboard and mouse input. Press the right-hand control key to release the mouse and keyboard from VM control.
Running programs has a 100% compatibility rate, meaning everything will work. This is because the programs are actually running under Windows. However, due to the nature of Virtual Machines, there is a performance penalty, depending on your system. Most Mid- to High-end System76 laptops and desktops will run Windows and most applications just fine, but there are other applications, like computational software or games, where performance is critical. In this case, a better bet might be Setting up a Dual Boot with Ubuntu and Windows.