Redsn0w 0.9.5 Jailbreak for iPhone is avaliable for Windows

Great news for Windows users, The iPhone Dev Team has just released Redsn0w 0.9.5 to support Windows, Now all Windows users can jailbreak their iPhone 3G/ iPod Touch 2G running on iOS 4 GM, it's the same as the last release of Redsn0w 0.9.5 which added multitasking and wallpapers, the only difference that the new version supports Windows.
Note: You should stay away from this release if you are on a carrier unlock as mentioned in the Dev Team official site.

The redsn0w beta has been updated for 4.0GM on iPhone 3G and iPod touch 2G (non-MC version). Multitasking and homescreen wallpaper are turned on by default (Apple doesn’t normally allow this on these 2 devices). You can deselect these features if you choose.

A version for Windows is now provided.

Just like our other betas, this one intentionally doesn’t “hactivate” the iPhone. Please wait for Apple’s public release of 4.0 for that part of it.

YOU SHOULD STAY CLEAR OF THIS BETA SOFTWARE IF YOU RELY ON A CARRIER UNLOCK. That’s because the beta redsn0w works only if your device has already been upgraded to the stock 4.0beta1/beta4/GM IPSW from Apple, which contains a baseband update. If you installed that IPSW, you’ve already lost the carrier unlock until the next planned release of ultrasn0w and blacksn0w.

To Jailbreak your iPhone 3G/ iPod Touch 2G you can follow the Step by Step guide posted here as it's the same instructions as the previous release.
To Download Redsn0w 0.9.5 beta 5 which supports Windows just check the links below:
Download Redsn0w 0.9.5 for Windows
Download Redsn0w 0.9.5 for Mac