OS Fonts affected by Font Navigator

My problem is Font Navigator keeps a certain number of Fonts "installed" (at hand).
I am of the understanding this is a way of lightening the load...having less Fonts installed at any one time.

When I open Font Navigator and install a new Font in my available Fonts list, a Font is removed/replaced.
I am unsure of how the choice is made, I assume its the oldest installed Font in the list, I don't know.
But a Font will disappear from my drop-down list of available Fonts (in Coreldraw).

This would be annoying if it wasn't for the the feature of Corel temporarily using necessary Fonts when opening a Document.

However, I am finding that Fonts in other programs are changing as a result.
For example, browser fonts switch to unacceptable choices.
Fonts used in my Email program are different, and unacceptable.
The font I am seeing right now, as i type this, is an Arial Black Bold type. lol

Even Fonts in the Coreldraw workspace change.
Some things become very hard to see, because some fonts are just too small or fancy.
The Corel Splash/Welcome screen has a very small, serifed Roman style font now.

In fact, just the act of opening Font Navigator when another program is running,
will change certain Fonts in that program.
I always close down everything before I use Font Nav.

I am guessing that Font Navigator is removing/replacing original OS installed Fonts. Why?
I have tried to put Fonts back, but without knowing exactly what Fonts are supposed to be there...
I can increase the number of allowed Fonts in my Font Navigator list, but this still doesn't put back anything already replaced.
I don't know what OS fonts have been changed.

Some advice?