Yahoo Answer:
"Not sure about changing the screen resolution, but make sure you click '800x600' when the game launcher comes up. To run in windowed mode, make a shortcut, then right-click and select properties. By the heading 'target' add '-w' (without quotation marks) after a space at the end of the text.
"C:\Program Files\Maxis\The Sims\Sims.exe" -w
Hope this helps

"
Works =]