Workaround for KB 887212

... or "You cannot join your computer to a domain in Windows XP Media Center Edition 2005"

Source: http://forums.whatpc.co.uk/thread.jsp?forum=6&thread=52646
Posted by: don h

Problem: KB 887212
Added: 2006-05-29

Joining a domain within' Media Center 2005
Happy new year. Oh and creamhackered, could you not come up with something better than 'DLL Patching Hero'?

IMPORTANT NOTE: Tekmaven brings up a valid point -- Those that join a domain with Media Center 2005 will not be able to use extender devices due to the Fast User Switching dependency (who uses extenders anyway?)

UPDATE (January 8th): I have received news the Linksys MCE Extender device works fine when joined in a domain.

UNIMPORTANT NOTE: Yes, I know this is somewhat painful for us lazy folk. If you want to pick up where I left off, go patch netapi32.dll, lsasrv.dll, netid.dll (and more?) to ignore the IsLegacyMce value (beware of future hotfixes). Or maybe you could write a nifty restricted-registry-key-permission-bypassing-mabob to make this change on the fly? 

Insert Windows XP CD.
Start > Run > X:\i386\winnt32.exe /cmdcons
(replace X: with the appropiate drive letter)
Acknowledge prompt by clicking 'Yes'.
Skip updating process by clicking 'Cancel' or by pressing 'Esc'
After installation, acknowledge success msg. by clicking 'Ok'
Start > Shutdown > Restart
At boot menu, select 'Microsoft Windows Recovery Console'
Select proper installation to log onto (default: 1) and press 'Enter'
(If prompted, enter Administrator password and press 'Enter')
Type (without quotes) and press enter: 'cd system32\config'
Type (without quotes) and press enter: 'copy SYSTEM C:\'
Type (without quotes) and press enter: exit
At boot menu, select 'Windows XP Media Center Edition'
Log into Windows and play a game of minesweeper (very important)
Start > Run > Type: 'regedit' and press enter
Click on 'HKEY_LOCAL_MACHINE'.
File > Load Hive...
Browse and select C:\SYSTEM
Specify key name 'BANANA' and click OK
Expand: HKEY_LOCAL_MACHINE > BANANA > WPA > MedCtrUpg
On the right-hand side, double-click IsLegacyMCE value
Change selected value to 1 and click Ok. (THAT IS NOT AN L!)
Click on BANANA subkey (under HKEY_LOCAL_MACHINE).
File > Unload Hive. Confirm.
Start > Shutdown > Restart
At boot menu, select 'Microsoft Windows Recovery Console'
Take sip of Dr. Pepper (very important)
Select proper installation to log onto (default: 1) and press 'Enter'
(If prompted, enter Administrator password and press 'Enter')
Type (without quotes) and press enter: 'cd \'
Type (without quotes) and press enter: 'copy SYSTEM C:\WINDOWS\SYSTEM32\CONFIG\SYSTEM'
(Yes, you want to overwrite - Go ahead and do it)
Type (without quotes) and press enter: 'del SYSTEM'
Type (without quotes) and press enter: 'exit'
At boot menu, select 'Windows XP Media Center Edition'
Take a **** while you wait.
Join domain. What, you were expecting instructions on this too?
(Pfft!)

Thanks goes to Chris123NT, Dyne, Creamhackered, LispyGlitter2, and ChaoServer (why is he here?) for unknown reasons.