What is the best way to find out where notepad.exe and mspaint.exe are that will work across various versions of Windows?
Should I get the Windows directory via SHGetFol
Normally, you would just execute them. They are on the system path in every version of Windows.
You can use ExpandEnvironmentStrings. The environment variable you want to expand is WINDIR.
WINDIR
In the past you could have used GetWindowsDirectory or GetSystemDirectory, but I think they are deprecated.
GetWindowsDirectory
GetSystemDirectory