iH8sn0w has released Sn0wbreeze, the Windows version of the Pwnage Tool for iPhone 3G and iPhone 3GS to update and jailbreak the iPhone with iOS 4. Sn0wbreeze allows you to create custom firmware (.ipsw file) so that you can update and jailbreak your iPhone on iOS 4.

Sn0wbreeze support the following iDevices :

    *      iPhone 3GS
    *      iPhone 3G
    *      iPod Touch 2G


Note: Backup your iPhone before jailbreaking with PwnageTool . 

iPhone 3G users can enable the multitasking and custom homescreen wallpaper features using Sn0wbreeze, which are officially not available in iOS 4.

Do let us know how it goes.