Yep, everything but outlook can have two instances. Outlook 2007 will be removed when you install 2010. unless you install new then old version... But then the versions will 'fight'.
Although I don't know what you will gain with 2007... 2010 is a solid improvement over 2007 while preserving the formats the same
And 2010 can save files as previous versions
possible, but not supported. id use just 2010 in your case. ive seen some people have office 2010 installed and need access 2003 for some old databases. why do you need both, since those two versions are so similar?
Are you just guessing or telling from the experience?you cant install 2007 with 2010 because they are practically the same. but can install 2007 with 2013 without any problem.