Windows XP Mode with Dual Monitors - Applications Not Appearing Correctly
Solution 1:
I'm not sure if it will work but have you tried UltraMon?
http://www.realtimesoft.com/ultramon/download.asp
Solution 2:
Actual Window Manager is the best window manager with multi-monitor support (by a country mile) i have yet seen, and i have tried a lot.
Actual Window Manager is shareware, try before you buy (60 days evaluation period).