You can use both 2004 and 2010 on the same computer - I do, also 2009 - if that is the point of your question. Also 2004 custom content can be imported into 2010 (again I do) although some slight amendments may be needed. However, although I have not tried, I believe importing from 2010 to 2004 is not possible. Most of my content on the DLS was made for 2004. Now, anything I make ( not much so far) is made in two versions - one for the DLS using as a minimum build 2.7, another using 2.4 uploaded to TPR.
Ray
