Before I start, I want to wish everyone Happy New Year. Wish you all have a blessed year ahead. I got iPhone 4 as Christmas gift. I was so excited, as always, over a new “toy”. First thing that crossed my mind was jailbreaking it.

What is a jailbreak?

Jailbreaking is a process that allows iPhone, iPod Touch and iPad users to install any applications that available without having to make a purchase. A jailbroken i-device can still use the App Store, iTunes and other normal function. Jailbreaking doesn’t slow down the i-device or use any extra battery power. There are no risk for jailbreaking, as you can easily use iTunes to restore your i-device to the default factory settings.

There are two kinds of jailbreak, tethered and untethered. An untethered jailbreak allows the i-device to be completely shut off and rebooted without the use of a computer. On the other hand, tethered jailbreaks can not boot by itself. So if it happened that the i-device was completely running out of power and being forced shut down, the reboot would only be done with the use of a computer.
There are no advantages to a tethered jailbreak. It’s just that when the developers release the applications, the tethered ones come first, then the untethered. So if you don’t want to wait, you just have to go with the tethered jailbreak.

UPDATE : Untethered Jailbreak is now Available

How to jailbreak iPhone 4?

Since what I got is the iPhone 4 running iOS 4.2, this post is about jailbreaking the iPhone 4 running iOS 4.2 or iOS 4.2.1 using Windows. If what you have is another type of iPhone or iOS, you just have to download the application that suit with your i-device then follow method below. You can find several links for several i-devices in the bottom of this post.

WARNING: Do this at your own risk. I am not responsible for any problems that may occur as a result of following this guide.

By the way, if your iPhone running iOS 4.0.1 or older, you can jailbreak directly from your iPhone. All you have to do is visit JailbreakMe.com from your iPhone browser, then follow their steps. It only works with iPhone running iOS 4.o.1 and older.

Warning: Below is the guide of a tethered jailbreak and you need to worry plugging in your iPhone 4 to computer on every restart.

Before we get started, you have to download the following :

• Latest iTunes
• iOS 4.2.1 for iPhone 4
• Redsn0w 0.9.6 b4 for Windows

The process of all the downloads above will take some time. After finished the downloads, connect your iPhone 4 to the computer.

• Upgrade your iPhone 4 to final build of iOS 4.2.1
• Launch Redsn0w and click Browse

• Select iOS 4.2.1 for iPhone 4

• Click Next and Redsn0w will start preparing data to jailbreak the iPhone 4

• Check “Install Cydia” and “Enable battery percentage” and click Next
• Turn OFF the iPhone 4

• Follow Redsn0w’s instructions to get iPhone 4 into DFU mode then wait until it finishes the installation. When it’s done, the iPhone will reboot, then you will have a jailbroken iPhone 4.

How to reboot a jailbroken iPhone 4?

If you need to reboot the iPhone 4, just follow the beginning steps above then check “Just boot tethered right now”

If after the jailbreaking you found Cydia in white icon, just reboot your iPhone 4. It would solve the problem.

And here are some options to download for other than what I used above :

• iOS 4.2.1 for iPhone 3GS
• iOS 4.2.1 for iPhone 3G
• iOS 4.2.1 for iPod Touch 4G
• iOS 4.2.1 for iPod Touch 3G
• iOS 4.2.1 for iPod Touch 2G
• iOS 4.2.1 for iPad
• Redsn0w 0.9.6 b4 for MAC

Next check out How To Download Application After Jailbreak iPhone 4