Just days ago a new version of SnowBreeze got released which added support for jailbreaking iOS 5.1 running A4 devices using Windows platform. The procedure can be a little tricky so for complete steps, see the step-by-step guide below after the jump.
Procedure: How To Jailbreak iOS 5.1 Running A4 Devices Using SnowBreeze
STEP 1: Download the latest version of Snowbreeze (i.e 2.9.2) [Download Link] and open it.
STEP 2: Place your device in DFU mode and browse the iOS 5.1 firmware for your device from the jailbreak utlility.
STEP 3: After selecting the firmware version, click simple mode from options so that Snowbreeze is able to a custom firmware file and place the custom made firmware file on any location (usually the desktop)
STEP 4: After the custom firmware is built, put your device back in DFU mode and click start to put your device in PwnedDFU mode.
STEP 5: After that open iTunes, hold the shift key button and click restore. Select the custom firmware made through SnowBreeze.
STEP 6: If the restore procedure is successful, you’ll see a Cydia icon on your home screen (usually on the second page). If it’s so, place your device back in DFU mode and locate/execute the iBooty file from the iBooty folder and select your device from the menu and click start.
Once the process is complete the main home page screen will appear and then you’ll be able to operate your jailbroken deivce. Remember, whenever you reboot your device, you’ll have to perform step 6.