can you copy a library from one location to another and overwrite the old one?

This is the problem, I have an old libray on N:\dir1\prglig\... I have a modified libray with new classes on C:\dir1\prglib\...

When I copy and paste the new library to n:\dir1\prglib\... and open it up the old libray is there not the new one. I don't know why this happens.

I know I can do an add class or drag and drop classes, but can I just copy a library from one area to another and overwrite the old library and bring over all of the classes?