What determines which monitor a program will open up on in a dual monitor setup?

"Windows 'remembers' the last position of a window and will start it right there the next time, or so the theory goes.

i do, however, recommend a decent window manager, allowing to apply rules (such as position alignment, transparency, etc.) to a program window.

Eusing's Auto Window Manager is free

My recommendation would be Actual Window Manager (shareware, $49.95, 60 days evaluation period), a 'must have' for multi-monitor environments."