You can perform Spirit untethered jailbreak on iPad, iPhone and iPod Touch firmware 3.1.2, 3.1.3, or 3.2. Follow the given instruction to jailbreak iPad with Spirit in Windows.
Download Spirit file for Windows.
Windows 7 users must set the compatibility mode to run this Spirit file (if you not using Window 7 jump to step-4).
Right click on downloaded Spirit file and select “Properties” option
Click on “Compatibility” tab and select “Windows 98 / Me” option from dropdown as shown below in screen shot and click OK button.
Double click the Spirit file to run it and connect your iPad with computer.
Click the Jailbreak button to start jailbreaking iPad.
After a while Spirit will prompt with Success message, Click “Quit” button.
iPad will reboot and finish the process, Finally your iPad will be jailbroken wiht Cydia installed.
See also: iPad tips and tricks