Windows on Intel Macs
There are presently several alternatives for running Windows on Intel Macs.
1. Install the Apple Boot Camp software. Purchase Windows XP w/Service Pak2, Vista, or Windows 7. Follow instructions in the Boot Camp documentation on installation of Boot Camp, creating Driver CD, and installing Windows. Boot Camp enables you to boot the computer into OS X or Windows.
2. Parallels Desktop for Mac and Windows XP, Vista Business, Vista Ultimate, or Windows 7. Parallels is software virtualization that enables running Windows concurrently with OS X.
3. VM Fusionand Windows XP, Vista Business, Vista Ultimate, or Windows 7. VM Fusion is software virtualization that enables running Windows concurrently with OS X.
4. CrossOver which enables running many Windows applications without having to install Windows. The Windows applications can run concurrently with OS X.
5. VirtualBox is a new Open Source freeware virtual machine such as VM Fusion and Parallels that was developed by Solaris. It is not as fully developed for the Mac as Parallels and VM Fusion.
6. Last is Q. Q is a freeware emulator that is compatible with Intel Macs. It is much slower than the virtualization software, Parallels and VM Fusion.
Note that Parallels and VM Fusion can also run other operating systems such as Linux, Unix, OS/2, Solaris, etc. There are performance differences between dual-boot systems and virtualization. The latter tend to be a little slower (not much) and do not provide the video performance of the dual-boot system. See MacTech.com's Virtualization Benchmarking for comparisons of Boot Camp, Parallels, and VM Fusion. Boot Camp is only available with Leopard or Snow Leopard. Except for Crossover and a couple of similar alternatives like DarWine you must have a valid installer disc for Windows.
You must also have an internal optical drive for installing Windows. Windows cannot be installed from an external optical drive.