Transfering Pro Tools sessions from studio to studio!!!!

[clinka]

I got a guy that wants me to mix like 12 songs for him. They were all done in Pro Tools but on version 6.9 and also on a PC. I will be mixing the cuts at home with my Pro Tools but I have 7.3 and I also have a Mac. I have a couple questions as to how to get the Pro Tools sessions loaded into my system. Correct me if I am wrong but think the first thing my friend has to do is do a "save session as". I know also that he will have to "enforce Mac\PC compatibility". I notice that when I have the dialog screen up for "save session as" that when the session format is set to latest that the "enforce Mac\PC compatibility" icon gets greyed out. Also when I choose the session format option to be Pro Tools 5.1 thru 6.9 that the "enforce Mac\Pc compatibility" icon becomes avalible again. Why is this? Does my friend with the 6.9 or 6.4 session need to save copy in before he sends the session to me? Also when he does it does he need to enable the latest tab under session format or the 5.1 to 6.9 tab. I know he has to check the "all audio files tab so that is not a problem. Thanx in advance to anyone responding to my post. Clinka