What is the name of the Dataset I am running?
When you run MYM, on the Main Menu, at the bottom, it should tell you what the name of the dataset MYM is currently running. This corresponds to a folder under the MYM12 folder on your hard drive. For Example: The dataset that is running when I run MYM is called "CURRENT". That means that there is a folder under my MYM12 folder which is also named "CURRENT" (c:\mym12\current).
If you want to run a specific dataset, you can choose Open Dataset from the File menu. If you want to run MYM and launch a specific dataset at startup, type "MYM [dataset name]" at the DOS prompt to load the dataset directly.