A simple save as will do the magic.
when you go to save as there is 3 options available in the lower left side.
1. save as
2. save as and continue (it will save as the part to user specified location then the previous/original part will be opened.)
3. save as and open (it will save as the part to user specified location then the new part will be opened along with the original part in the background)
In addition to mention by others, you can do it another way:
Have a copy of the original file and change the name of it, and open and alter it.