To launch Parallels Desktop you have two choices. However, version 7 of Parallels includes a security barrier to ensure there is absolutely no risk. There's no need to worry about viruses on your Mac by running Windows in Parallels Desktop - any viruses will be restricted to the virtual environment that Windows operates in and won't affect your Mac in any way. The Transporter feature guides you through the whole setup process, asking you if you'd like to be able to share files between OS X and Windows and use external devices amongst others.
Parallels Desktop will then install Windows in about the same amount of time that it would take to make a fresh install of Windows on a PC. You'll either need a copy of Windows on CD to install it or an ISO image will also suffice. Setting up Parallels Desktop is a breeze. With the former, you'll get quicker and more realistic results but there's no substitute for being able to switch at will between OS X and Windows which is what Parallels Desktop allows you to do.
There are essentially two options to run Windows on the Mac - using Boot Camp which involves installing Windows on a separate partition and rebooting it in Windows or, running Windows in a virtual environment, such as the one that Parallels Desktop provides. Parallels Desktop 10 A more convenient alternative to Boot Camp Long gone are the days when you had to choose between Mac or PC - now you can have your cake and eat it with Parallels Desktop 8.0 which allows you to run Windows and other operating systems within OS X.