EDIT: Be aware, Sn0wbreeze is not an official Dev Team release, and doesn't include the standard kernel patches and the sandbox issues aren't sorted out. This means certain things could be broken on it (Safari, Cydia, etc). We still recommended you use official Dev Team releases.

Two of the most popular jailbreak tools have been updated so that users who wish to jailbreak their iOS devices on 4.3.1 can now do so. Both PwnageTool, the iPhone Dev-Team's jailbreak solution, and Sn0wbreeze, a windows jailbreak tool developed by @ih8sn0w, now have beta releases that enable a tethered jailbreak for all iOS devices (excluding the iPad 2).

Redmond Pie has already posted a tutorial on how to have a "semi-tethered" jailbreak on iOS 4.3.1 using PwnageTool.

http://modmyi.com/forums/iphone-news...c-windows.html