Just go to START button, then ALL PROGRAMS and start Excel from there. This opens up a new instance of Excel in a separate Window in Win 7 Excel 2010
The procedure from Oregon74 (and others) works well, especially if you're an occasional user.
However, if you're in and out of the program numerous times daily - such as many accounting folks are - then the extra mousing/keystrokes can become a bit cumbersome. Just modifying the DDE adjustment in the Excel settings seems to only work in some situations,
but while the comprehensive registry mods that apply to the various versions are more cumbersome and exacting to implement, the result seems to work very consistently well - for me, at least. My mods included a long history of upgraded versions, including
Office 2003, 2007, 2010, and 2013.
I haven't had any trouble since.