Last week, the first untethered jailbreak for iPhone 4S and iPad 2 was announced — but it only worked if you ran OS X. Forunately, the Windows version is now ready.
The tool, built by Greenpois0n and called Absinthe, works on the iPhone 4S running iOS 5.0 and 5.0.1 and the iPad 2 running iOS 5.0.1, and it will either work really well or you'll end up bricking your device. Still, worth a try. You can download the Windows version of Absinthe. More here.