These are instructions on how to perform an untethered jailbreak of your iPad 1 on iOS 5.0.1 using RedSn0w for Windows. The Mac version of this tutorial is here.
Create a folder on your desktop called Pwnage
Download the latest RedSn0w from here and place it in the Pwnage folder. Likewise, download the 5.0.1 firmware from here and place it in the Pwnage folder. (Note: you do not need to download the 5.0.1 firmware if you are already on iOS 5.0.1)
Extract the RedSn0w zip file by double clicking it.