when I set my files to save as 2007 in the options dialog box, then click save in my working file - ACAD tells me it is unable to save because "one or more objects in this drawing cannot be saved to the specified format. The operation was not completed and no file was created." So......WhatIgather is that if you utilize ACAD 10 for any of the added features you will be unable to share / communicate with others? The file i am trying to save is a practice session for me, I only have two entities in the drawing file. One is an imprted table from excel and the other object is a block of a W beam that has added constraints to it. Both items are in model space. I would hope you could utilize these items in previous versions? Well, anyway this just further stops me from using ACAD 10, I've had it since March or April and the last time I tried using it, I had file saving issues - then it was: if I saved my file in 2010, even though I had it defaulted to save in 2007, I was unable to open it up in 2008 and 2009. I've talked a few people and no one seems to have this problem - so I'm thinking it's just me. Either way seems 2010 keeps burning me everytime I touch it. There are some features to 2010 that I would like to become accustomed to but using it in the real world just has too many issues for me.