Office 2003/2010 on same machine--How can I stop 2010 hijacking file defaults?

[Algee]

I bought and installed Office 2010 because a client insisted that 2003 was no longer secure after MS ceased support.

I hate the look and feel of 2010, especially the space-hogging ribbon, and its lack of user adaptability. I hate its steep learning curve with no real benefits over 2003. So my strategy is to create my work in 2003 and re-save final versions in 2010 for the client in question.

Unfortunately, every time I open 2010 it hijacks all Office file defaults, and I then have to reset them using Detect and Repair in 2003. The first time I installed it also hijacked Normal.dot without creating a backup and obliterated all my keyboard shortcuts and Autotext entries (Thanks MS), so I now have two separate Normal.dots in different directories.

Is there any way to make Office 2010 mind it's own business and leave my settings alone?