How do I transfer my files to another computer?

Back them up on one computer as explained here:

http://support.mastercook.com/entries/82783855-MasterCook-15-Backup

Then merge those backed up files into MasterCook 15 on the other computer as explained here:

http://support.mastercook.com/entries/82512489-MasterCook-15-Merge

Please keep your files backed up on a regular basis.