Hi SunilB,
You don't want to copy the *.mm4 file for this. You can use the Portfolio Editor window to copy/paste a sub-portfolio. When you do this, it will put another copy of all the same investments into the new sub-portfolio. This means you'll have 2 copies of each of these investments open. They are the same investment, so when you make an edit, it will show up in both places. You have 2 instances of the same investment file. Maybe this is what you want, I'm not sure. If you want them to be the same, this would work. However, if you are planning to record different transactions in each, then you don't want this. In that case, you need to create a 2nd investment file, so you have 2 investment files, and each one is only open once.
For help on using the Portfolio Editor, I'd suggest watching the
Portfolio Editor Tutorial and also the
Sub-Portfolio Tutorial.