If this is from Panasonic Toughbook support website, then you need to unzip it (twice?) with 7zip until you have the complete folder structure.
I'm not inclined to fiddle with the Toshiba software.
These are original Panasonic drivers minus Panasonic drive requirement.
What would happen to my existing drivers. What would work or not work?
Depends. If there is an older version of the Panasonic drivers installed, then you will be asked if you want to update them. Assuming you have different software like InCD or Roxio's equivalent (Drag-to-Disc etc) installed, then it is better to get rid of that before you install the Panasonic drivers.
Obviously my W2000 has a DVD-RAM driver because it can write and read.
Then there is 3rd party software installed.