We're looking for games along the line of Myst or Riven or other fantasy role explorer puzzle games. We got an old shuttle X computer running win 2000 so I imagine it aint able to handle the more graphics intensive games they probably have out there now.

Myst or Riven are the only ones I know of (Riven as of just now). It isn't exactly a widely develloped genre.

There is Portal, but that might not work on your computer. Could try Narbacular drop.

If you're looking for adventure games along the lines of Myst and Riven, might I suggest:

Atlantis: The Lost Tales
Beyond Atlantis
Atlantis III: The New World
The Journeyman Project Turbo
The Journeyman Project 2: Buried in Time
The Journeyman Project 3: Legacy of Time
Myst III: Exile (might run)
Timelapse
The 7th Guest
The 11th Hour
Amerzone: The Explorer's Legacy

And some 3rd person perspective games with a theme you might enjoy:
The Longest Journey (It's sequel Dreamfall: The Longest Journey might not work)
Syberia
Syberia 2

Note: I haven't played them all, but people around me who like the games I think you described played and enjoyed them.

You might want to check the reviews on Just Adventure + (http://www.justadventure.com/).

The Witcher is truly good game.
Remember that when you upgrade your computer.