Preview changes using excel 2007/2010 on a Windows XP machine and a windows 7 machine.

Hi, I was wondering if anyone could help diagnose my problem.

I have a set of excel files (xlsx), that are updated and saved by 3 different individuals. We were experiencing some major formatting changes when viewed and printed off of different machines, which were causing us some major headaches. The formatting was mainly charts and picture positioning and layout.
Firstly, I was running Office 2010 on a windows 7 pro machine. The other 2 people had Office 2007 on windows xp. I then installed Office 2007 on my windows 7 machine, and things were better initially, but then started going haywire again.
I finally had to get a new laptop with windows xp and Office 2007 to exactly match what the other persons have, just to update these files. This is the first week I am doing this.

Is it because of the Windows version differences or because of the Office 2007/2010 differences?

Thanks

bumping...anyone have any ideas?