Not recognizing monitor

[Rollie]

Installed Knoppix 6.4.3 on Dell GX240
It has an ATI Rage 128 video card, connected to a Viewsonic PS790 Monitor.

The Rage 128 card appears to be recognized ok, but it doesn't see my monitor and
instead uses a default with a resolution of 800x600.

What can I try to resolve the problem?

[utu]

First, try Main menu/Preferences/Monitor Settings.
See if you have any choices there.