How to unlock/lock the HTC EVO (Sprint) bootloader

A common problem that may occur while you are trying to “unchain” your phone is related to its bootloader. Therefore, if you want to root, or install new ROMs (such as Cyanogen’s mod) on the HTC EVO you should first know how to unlock its bootloader. Don’t worry, the process is simple and below you have a step-by-step guide in which you will find all the information needed in order to succeed. Also, the procedure can be applied from a Mac OS X or Windows running terminal, so you shouldn’t have any issues in completing it.

When released, all the phones have the bootloader locked, so it is like a default setting. The only way in avoiding this is if you can buy an unlocked phone straight from Google, but this is happening rarely. Now, as you may know, the Android OS is an open source project, meaning that the manufacturer was able to change, or personalized it. Fortunately, this fact will not have any influence on the way we will unlock the Sprint EVO bootloader, the process being the same for most of the handsets (see our previous posts where we have done the same thing for the Nexus S, or Nexus One).

In a few words a phone bootloader is very similar with a computer one. When the device is first powered on, it usually does not have an operating system in ROM or RAM. That’s why it must execute a small program stored in ROM and a few data in order to access the nonvolatile devices from which the operating system programs and data are loaded into RAM.

This “small program” is also known and named as bootloader or bootstrap loader and its only job is to load other data and programs which are then executed from the RAM memory. Also, the program is different from one OS to another; for example the Android one is completely different from the one included on iOS, MeeGo and so on.

Another important aspect that you must know is that once you unlock the bootloader you will void your EVO warranty. So if you’re not comfortable with this you should probably stop here. Anyway, in the end of the guide I have showed you how to lock it back, this if you will have to take you’re handset back to the carrier. The procedure will wipe the data from the EVO, so I strongly recommend backing it up before you start doing anything.

Now, here are the things we are going to need in order to succeed with this step-by-step guide: a computer running Windows, Linux or a Mac and an USB drive. Also, fastboot should be installed on the computer. If not, you should check our previous posts and install Adb on Linux / Mac or install the Android SDK on Windows. After competing this, you can turn back and follow the steps below.

How to unlock the bootloader on a HTC EVO

1. Turn off the smartphone.
2. Then, hold “Volume Up” and “Power” buttons until the bootloader appears.
3. Connect the device to a computer using the USB cable.
4. On the computer, open the terminal / command prompt (for windows just go to Start-> Run-> type cmd.exe-> hit Enter).
5. Type “fastboot oem unlock” and hit Enter.
6. Agree to the warning sign, by selecting the answer with the Volume keys and confirming with Power.
7. The phone will reboot.
8. That’s it.

As you can see the guide was very easy to follow and complete, but if you had any kinds of issues share it with us so we can clear it up. I also know that I promise that I will show you how to lock the HTC EVO bootloader back, so here you have it: just redo the steps 1-4 from above and instead of introducing “fastboot oem unlock” type “fastboot oem lock” and you are done.