The great Stefan Münz is right when he says that you can't simply replace NOTEPAD.EXE on Windows 2000.
But he is wrong when he says that it is impossible.
Below is how to do it (stolen from Ultraedit's Notepad replacement at ftp://ultraedit.com/notepad.zip). There is nothing special with the Ultraedit NOTEPAD.EXE, it's a simple Windows EXE. The whole trick is to avoid the automatic recovery of the file protection built into Windows 2000 and similar.
Tux2000
INSTRUCTIONS FOR REPLACING NOTEPAD WITH ULTRAEDIT-32:
Some applications automatically call Notepad without offering the user
any options as to which utility to use. If you'd like UltraEdit-32 to
replace Notepad in these instances please follow these steps:
1. Make sure that during installation of UltraEdit you select the option to
have UltraEdit added to your path. If you did not do this you can reinstall
UltraEdit-32 or edit the path to include the directory to which you installed
UltraEdit-32. Please don't ask us how to edit the path, if you are
unsure please reinstall UltraEdit-32, your configuration changes will not
be lost.
You can verify UltraEdit-32 is in the path by opening a DOS Command Window
and from a DOS prompt (NOT in the UltraEdit directory) type "uedit32". If
this starts UltraEdit-32 the path is set correctly. If not, you will need
correct the path as outlined above.
2. To replace notepad.exe we STRONGLY recommend you find all occurences of
notepad.exe and make a backup copy of them. Do not rename them as this may
cause the File Associations to notepad.exe to remain with with the renamed
file.
After making a copy of the notepad.exe replace the notepad.exe with the
included file (notepad.exe). This file (notepad.exe) will invoke UltraEdit
in instances which by default call for Notepad.
WINDOWS 2000 NOTEPAD INSTALLATION INSTRUCTIONS
** Note - You need Administrator access to make these changes (at least
with a properly configured system).
1. In the WINNT\system32\dllcache directory, rename the old notepad.exe
(if it exists) to notepad.exe.bak or something similar so that you'll have
it if you need to go back. (This directory may be hidden.)
2. Copy the attached notepad.exe into your dllcache directory. Windows 2000
will notice the change and pop up a dialog box asking you to insert your
Windows 2000 CD so that it can restore the file. Hit <Cancel>. You will be
asked if you're sure that you want to use the unsigned version; answer <Yes>.
3. After Step 2, you can go ahead and copy your new notepad.exe into
your WINNT and WINNT\system32 directories. You'll get the same dialog
boxes that you did in Step 2; just give the same responses. You're now
ready to roll. (If you do this before Step 1, Windows 2000 will take its
original copy from dllcache and replace your new versions.)
** Note that if you have your Windows 2000 CD in your drive when you do this,
it's possible that instead of popping up a dialog box, Windows 2000 will pull
the old notepad.exe from the CD and replace your new notepad.exe
without any notification. If this occurs, it won't hurt anything,
you'll just have to take the CD out and re-do Steps 1 and 2.