Hacking the HTC TYTN II (a.k.a. Mda Vario III, Kaiser, AT&T Tilt) is fairly simple as long as you follow a couple of steps in the right order.
In this hack we'll first prepare the phone so that it can receive a new ROM. There are quite a few people making ('cooking') ROMs for this phone. Each different ROM usually contains a lot of pre-installed software, sounds and graphics, but the biggest difference between te ROMs is mostly the interface.
When the TYTN II first was released, it came with window mobile 6.0 installed. The latest ROMs have windows mobile 6.5 in them. Step One
First step is to unlock the phone, so it can accept a new ROM. For this we need a little something called an SPL (Second Program Loader). There are two types of SPLs, Hard and Soft. A Hard SPL is one that is permanently flashed in your device memory and will boot up every time your device boots. A Soft SPL is a stand alone .exe that is run on your device from within the OS. It basically changes your OS from running Windows, to initializing the boot loader. A Soft SPL is only loaded into RAM temporarily and will not survive a hard-reset.
For changing the ROM on your phone you should using the HardSPL because most ROMs are dependent on specific HardSPLs. Your phone will not boot correctly otherwise. Therefore when you download a certain new ROM, it usually says in the info what HardSPL to use with it.
One example of such a ROM with HardSPL and Radio (we'll get to that) is found here
. On the xda-developers forum you'll be able to find plenty of ROMs so you an pick the one you like.