Here are the instructions on how to jailbreak your iPad 1 on the 4.3.3 firmware using RedSn0w for Windows.
First you need to create a folder on your desktop called Pwnage
Download RedSn0w from here and place it in the Pwnage folder. Likewise, download the latest 4.3.3 firmware from below and place it in the same folder.
4.3.3 (iPad 1): iPad1,1_4.3.3_8J3_Restore.ipsw
Extract the RedSn0w zip file into the same folder.
Connect your iPad to the computer and launch iTunes.
Select your devices on the left. Now hold down Shift and click the Restore button. Restore is preferred as it won’t create any wasted space on your iPad.
Navigate to the Pwnage folder on your desktop and select the 4.3.3 firmware ipsw. Click the Choose button to continue.
Open the Pwnage folder on your desktop once iTunes has finished updating your iPad to the desired firmware and launch the redsn0w application from the redsn0w folder we extracted earlier.
Open the Pwnage folder on your desktop
Select the 4.3.3 firmware ipsw from the Pwnage folder on your desktop then click Open.
Once the firmware has been verified click the Next button to continue.
RedSn0w will now prepare the jailbreak data
You can select the jailbreak options you would like. Make sure Cydia is selected and click the Next button to continue.
Make sure to plug your iPad into the computer and is OFF then click the Next button.
RedSn0w will now guide you through the steps to get into DFU mode.
Hold down both the Home button and the Power button for 10 seconds.
Now you can release the Power button and continue holding the Home button until RedSn0w detects the device.
RedSn0w will then begin uploading the new RAM Disk and Kernel.
Once this is complete you will be notified that RedSn0w is done. Click the Finish button. When your iPad finishes rebooting (5 minutes or so) it will be jailbroken with Cydia on the SpringBoard.