Here is a simple script that will automate the process of replacing notepad.exe with notepad2.exe in Vista.

I borrowed the idea from Jens Schaller and Lifehacker. Just save the code in a .bat file in the same directory as notepad2.exe and it will take care of the rest.

takeown /F c:\windows\notepad.exe
icacls c:\windows\notepad.exe /grant administrators:F

takeown /F c:\windows\system32\notepad.exe
icacls c:\windows\system32\notepad.exe /grant administrators:F

copy notepad2.exe c:\windows\notepad.exe
copy notepad2.exe c:\windows\system32\notepad.exe