os.system and flow control

[Lad]

In my program I use 
os.popen2('notepad.exe IDPass.txt')
to open IDPass.txt file in Notepad window. Users can edit this file
but the problem is that if the program runs on Windows 98  , the
program does not wait for closing of Notepad window but continues
running with the next command after
os.popen2('notepad.exe IDPass.txt').
If the program runs on XP, the execution of my program is paused until
I close the notepad window.
How shall I force the WIndows 98 to pause the execution like WIndows
Xp ?
Thanks for help
Lad