When I start New Game characters are almost invisible. Also, the mouse moves irradically. Help. Thanks, Louis.

It's probably a driver issue.
What video card is in your computer?
There might be some tweak in the video card settings that would help.

Try compatibility mode. Sometimes that helps with older games.

geoForce 9800

The Geforce 9800 is way more card than Thorgal's Quest needs.
Using compatibility mode might help.
Reducing graphics acceleration might help.
Also, the game was developed before computers had multi-core processors so assigning the game's affinity to a single processor might help.

Thanks,all. I'll try that.