The biggest advantage that GSM devices have over CDMA devices is the ability to switch from one carrier to the next, relatively painlessly and without always needing to switch your phone. Making the phone capable of that jump is commonly referred to as SIM unlocking the device, meaning you remove the carrier lock on the device which in turn allows it to accept SIM cards from any other carrier that uses the same frequencies. Technical details aside, users of the HTC Holiday, HTC Raider and HTC Vivid can now get in on the carrier swapping goodness, as they can now be SIM unlocked.
XDA Recognized Contributor cruzin_cruzing has posted a method that was originally created by XDA Senior Member sieempi for three other similar HTC handsets. The method itself routes users to sieempi‘s website, where some information needs to be entered. From there, a modified Config.dat file is emailed to the user. Users then put that on the root of their SD cards. From there, it’s booting into the bootloader, selecting the SIMLOCK option and awaiting the proper output.
At the end of it all, users should have a fully and completely unlocked phone ready for use with any carrier on compatible bands. The whole process takes only a few minutes and is rather simple. You will, however, need a SIM card from another carrier to verify that it has indeed worked.
To get started, head over to the original thread._________