The screenshot from Print Screen button "PrtScr" are to be found:
My Documents/My Games/King's Bounty/Screenshots
(if you run demo it would be : My Documents/My Games/King's Bounty Demo/Screenshots... but I am not sure if KG tL Demo supports screenshot making in the same extend)
also are in memory:
open any picture editing programs (Paint in Windows, but even cheap Photoshop 7.0 will do), click "NEW" and press CTRL+V (or CTRL+v ... as maybe some other oldscool detailist will press ctrl+shift+v when seeing CTRL+V
)