The first alternative is installing Windows on Boot Camp. Boot Camp is a feature on your Mac that allows you to partition your hard drive, to install Windows on your computer. Boot Camp is free. You will need to purchase a full Windows OS. Some stores and sites such as Amazon, Best Buy, TigerDirect, MicroCenter and other Technology stores may have the full OS. Once you purchase the Windows OS, follow the instructions on installing Boot Camp from Apple.
The second alternative is purchasing Parallels Desktop for Mac. This one is mostly popular and a few thereians use it currently. You will still need to purchase a Windows OS. Also, you will need to purchase Parallels. It can get expensive since you need to purchase both Parallels and Windows OS, but when you purchase Parallels you get to connect your Mac with Windows, without the need of logging off your Mac and logging onto Windows. It crosses path with Windows nicely, and it has had positive feedback when it comes to graphics and quality.
The third alternative is purchasing VMWare Fusion. Similar as Parallels Desktop for Mac. It pretty much does the same exact things. There are no difference between them. They both work nicely and great quality. You will still need to purchase a Windows OS.
Fourth alternative, you can get VirtualBox. It's free and developed by Oracle. It does the same thing as Parallels and vmware. It's not as popular like the others but it's been closely compared to.
Lastly, Crossover. A full page about it made by TheChaz can be found here: http://therecommunity.net/content.ph...-Mac-Crossover
You can read the comparison here: VMWare Fusion, Parallels, and VirtualBox