1. Windows
1.1. Pros:
1.1.1. Virtually all hardware manufacturers will offer support for a recent version of Windows when they go to market with a new product.
1.1.2. There is a huge selection of software available for Windows. This is both due to and the reason for Microsoft's dominance of the world market for PC computer operating systems and office software.
1.2. Cons:
1.2.1. Compared to other operating systems, Microsoft security is weak in security.
1.2.2. Few of Microsoft's support staff truly understand security or high-end enterprise issues, and even less have access to or understand any of the source code.
2. Ubuntu
2.1. Pros:
2.1.1. Ubuntu can be booted on a LiveCD, you don’t have to install it in your hard drive.
2.1.2. Ubuntu comes with Virtualization using Zen that allows you to run Windows on another partition hard drive.
2.2. Cons:
2.2.1. Can’t install most software because most software are built for Windows and not Ubuntu, this mean you will have to use emulators to install Windows software to make it work on your Ubuntu system. Also, there is no guarantee if the emulator will work perfectly or not.
2.2.2. Many Windows video games cannot be install with Ubuntu since it is not built for games.
3. Mac.OS X
3.1. Pros:
3.1.1. Easier to use for the non technical.
3.1.2. More secure than Windows due to its UNIX base.
3.2. Cons:
3.2.1. More expensive upfront than other choices.
3.2.2. Less hardware choices than Windows.