I have been successfully using my cookbook for a long time. However, suddenly the cookbook won't open. The screen says "Unable to locate the Cookbook: C:\Users\Public\DOCUME~1\MASTER~2\MYCOLL~\CookbookName.mc2.
This typically happens when the cookbook file on your computer becomes corrupt. That can happen for a variety of reasons unrelated to MasterCook. Generally a file becomes corrupt when a program is left running and that file is in use, and Windows crashes or restarts (automatic Windows Update). Generally any program that is left running and using a file is susceptible to corruption if the computer suddenly crashes or restarts.
If you have a backup copy of this cookbook, then you would want to use it instead. Copy your cookbook files from the backup location and replace the ones that are corrupt that the program is using. Do this when MasterCook is not running.
Please keep your files backed up on a regular basis. It is quick and easy. See MasterCook 15 Backup.
Follow these instructions: Corrupt Cookbook Files