My Solution

Hello to all HTC Smartphone users. HTC mobile phones comes with good hardware and great operating systems. Now, most HTC Mobile Devices are Android Powered. This tutorial is for them, who own an Android powered HTC device and want to unlock their devices booktloader.
First of all, let me make you clear about what is this bootloader and why you need to unlock it. HTC by default, Locked your device from any un-authorized access to core firmware. That is, you can not do any changes in your Operating Systems. If you are friendly with Rooting process then this Unlocking Bootloader is required to Root your device. After unlocking bootloader you can root your HTC device. So now, lets move to the actual procedure for unlocking your devices bootloader.

Disclaimer : Unlocking Bootloader may not available for your device, most probably if it is older than october 2009. So in steps below, when we visit the HTCDev website then select your device and if its not listed then select All other Supported Devices. Here, i am using HTC Desire C.You should read the and understand the risks and responsibilities at HTCDevs website. Do this at your own risk.

How To Unlock Bootloader Of HTC Smartphone :

1. Go to HTC Devs Website and Register there.(Click on the link given in step 3)
2. Verify your account by clicking on the link given in your email.
3. Now visit this webpage: Unlock Bootloader | HTC : http://www.htcdev.com/bootloader/
4. Check for your Devices Name on the right sidebar. If its not listed, select All Other Supported Devices. In my case, HTC Desire C is not listed, so i chosen All other Supported Devices.
5. Now itll ask you to login. Log in with the account that you registered before.
6. A pop up will ask you for confirmation. Read the message and click on Yes if you want to continue.
7. Now an another pop up will open, read and Accept the legal terms and click on Proceed to Unlock Instructions
   Now you can follow the instructions given there, in case you find them hard to understand, you can follow detailed step by step process given below.
8. Now you will have to download and install following tools:
   HTC Sync Manager (This is required for installing USB Drivers).
   Download Required Files : Download Bootloader Unlock and extract them to C:Android
9. Here comes the part, where we need to deal with your mobile. Switch Off your mobile phone. Remove the battery and put it in.
10. Press Volume Down + Power Button (Press Vol Down first and then Power button).
11. A Lcd will open saying ***Locked*** at the top. Highlight the FASTBOOT and press the power button.
12. Now connect your mobile to computer via USB.
13. Now navigate to the folder where we extracted files downloaded above.(C:Android)
14. Make sure there are following four files :
    adb
    AdbWinApi.dll
    fastboot.exe
    AdbWinUSBApi
15. Now Go to Windows->Run and type cmd and hit enter.
16. In Command prompt, type following:
    cd C:Android
    then type this: fastboot oem get_identifier_token
    Now a long text will be in cmd window.
17. Right click in the text and click on Mark.
18. Now mark all the text in between these two strings:
    <<<< Identifier Token Start >>>>
    and
    <<<< Identifier Token End >>>>
    Press Ctrl+C to copy selected text
19. Go to this page: Enter Identifier Token: http://www.htcdev.com/bootloader/unlock-instructions/page-3
20. Now paste the copied string in the box and click on Submit button.
21. Now open the Inbox of EMail address that you used to sign up or register at HTC Dev. Youll find an attachment there. Download it and save it in the same folder (C:Android).
22. In command prompt, type the following:
    fastboot flash unlocktoken Unlock_code.bin
23. Now youll see a disclaimer message on your phone. Read it and click on Yes if you want to unlock bootloader of your device. If you select No nothing will be done to your device and your phone restart normally.
24. Thats All...Now you have successfully unlocked the bootloader of your HTC Android Phone. Now you may proceed to Rooting and then installing a custom ROM like NameLess on your Mobile Phone.