MS office never maximises in just 1 monitor

Hi,

I have a dual monitor setup and I've recently updated to the most recent
Matrox BIOS and driver. Before the update, all my software would neatly
maximise in only 1 monitor. But now that I've updated, some software always
maximises across both monitors (which is annoying). I've tried tinkering
with every setting I can find in the Matrox Powerdesk without any luck. And
I've quickly looked for relevant settings in the registry but with no luck.

Please help! How do prevent programs from maximising across both monitors?

Here's my setup:

Windows XP Pro SP1
Matrox P750 (latest BIOS and drivers; stretch mode)
Dual Iiyama 17" analogue monitors

Examples of software that maximises in 1 monitor:
Internet Explorer 6
Notepad

Examples of software that maximises in both monitors (bad)
MS Office XP
Reference Manager

Thanks in advance,
Jack