Bootcamp is a software package Apple provides with each Mac OS X version. Bootcamp incorporates drivers and foundation software for Apple Mac hardware in Windows platform. You can set up a Windows partition from Mac using Bootcamp assistant. The most-recent variant of Bootcamp is 3.2 and is designed to work with Mac OS Snow Leopard. Apple is preparing to distribute Bootcamp 4.0 to in order to allow users install and dual boot Windows with the upcoming OS X Lion.
You can download Bootcamp 4.0 from the OS X Lion interface. Find the Bootcamp Assistant using Spotlight search (Or from Application folder>Utilities>Bootcamp Assistant) and open the app from the list. Click on continue and in the next window, select to download “Windows Support Software for this Mac” or Bootcamp 4.0, which is around 650MB in size. At the end, it will show option burn the file into to a CD or DVD.
In the next step, choose the required size of the Windows installation using the slider. Keep a minimum of 20GB for the partition and also note down its name and size. Now insert a genuine Windows 7 DVD and start installation.
Windows 7 setup will load files and after sometime it will list the available disk partitions. Pick Bootcamp and click on the Drive Options (check below) and then format it. Now continue Windows installation on this partition.
Insert the Bootcamp 4.0 CD after completion. Open up Windows Explorer and browse through the disk, and execute setup.exe inside the Bootcamp folder. The application will install Graphics, sound and other system drivers (for Intel iMac, MacBook Pro, MacBook Air) and necessary software for Apple trackpad, Bluetooth, Magic mouse and other peripherals. Restart the system after installation. Upon start, press the Option key (alt) firmly for a few seconds. The bootloader will show the Mac OS X Lion and Windows 7 dual boot options.
Installing OS X Lion 10.7 above Snow Leopard 10.6.8 will not delete your existing Bootcamp partition. As shown in the screenshot, after installation you will get Mac OS X, Recovery HD and Bootcamp options. But I recommend you to take backup and I won’t be responsible for any loss.