Yesterday, the Sn0wbreeze 1.6.2 version was released and it can fix the errors which many users faced during the jailbreak with Sn0wbreeze 1.6.1. The new version has been released to fix the iTunes Restore error, iBooks and Youtube on iOS 4.
You could download Sn0wbreeze 1.6.2 (link below) and jailbreak your iPhone on Windows using it. Read this guide to jailbreak your iPhone with iOS 4 using Sn0wbreeze 1.6.2. After that you could unlock it using Ultrasn0w 0.93. Read this guide to unlock your iPhone.
Download Sn0wbreeze 1.6.2 from here.