From what I've heard, you need to install the HW2Patch before installing doorsos, although apparently this patch is capable of screwing up your calculator.
Depending on the version of your calculator (hit F1 & select option A, "About" to see what version of AMS / HW you have), it may not work. Excerpts from DoorsOs documentation:
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This program suppresses the 8/24 kb (it depends on AMS) hardware
limitation : in clear, no more black bar !
This limitation is present on HW2 2.0x. HW2Patch works only on 2.01,
2.03 and 2.04 : use the about command (first menu, from Home) to know
the hardware and software versions of your calculator.
II) Installing HW2Patch
Launch HW2Patch. This offers you to patch the ROM definitively :
- if you accept, the ROM will be modified, then you won't need HW2Patch
even after a reset.
************************************************************************
WARNING ! You won't be able to send your product code to another
calculator.
************************************************************************
You can restore your ROM by a simple flash.
- if you refuse, you will have to launch HW2Patch after each reset, or
after the uninstallation of certain kernels.
NOTES: - WARNING ! Using this program isn't without danger. Be sure your
calculator is stable.
- Use this program at you own risk and I cannot be held
responsible for any damage done to your calculator.
Texas Instruments has implemented a restriction to assembly programs in Hardware Version 2.00 calculators, so here is what you have to do to break this restriction:
Have a look at the About Menu (Press F1 - A from the Home screen) to know your Hardware and AMS (Advanced Mathematics Software) version. If nothing is displayed about your Hardware version, it means you have a Hardware Version 1.00 calculator, so there is no problem 
* If you don't have a Hardware Version 2.00 calculator, there is no problem
* If you have a Hardware Version 2.00 calculator and AMS 1.05, there is no problem
* If you have a Hardware Version 2.00 calculator and AMS 2.0x, you must install HW2 Patch 2.10 by Julien Muchembled on you calculator before installing DoorsOS. You can find HW2 Patch in the HW2\HW2patch folder.
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Hope this helps...
HW2Patch should be in a folder in the doorsos zip file. If not, get it
here.
Not sure if I count as a "wizard" yet... just got the 89 friday night.
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