Every time I start a new game and create a party, the game just keeps the first party I created and it does not change. It doesn't matter how many members it is, it still keeps going back to the original party I made. Also deleted the save files and started over, but that original party keeps coming back.

Have you tried removing the members from the party 1 by 1? Then you can create new members in the empty places.

I had this problem, too.

Whenever I would create a new game, roll characters, and start, the game kept loading up with a single character, a mage named "test". I would get the intro narration, or the opening conversation with Hrothgar. It seemed to be loading a save game, so to resolve it, I found two places that I deleted the contents of the save game directory. They are (from memory)...

<user>\Appdata\Local\VirtualStore\GOG.com\Icewind Dale Complete\mpsave
and
C:\Program File (x86)\GOG.com\Icewind Dale Complete\mpsave

Once I delete the contents of that directory, I could start a new game with my rolled characters, and everything else seems to be fine.