You can install it as many times as you want as long as it's only on 1 computer at a time. You may need to call the activation line after 2 or 3 activations though.
Put the disc in, and change the boot order in the BIOS to boot off the disc. Remember to back up your data if there's anything you want to keep.
Before you do this, you'll want to make sure there are windows 7 drivers available for you hardware, and that your laptop meets the windows 7 hardware requirements.http://www.microsoft.com/windows/windows-7/get/system-requirements.aspx