Go to your options and check to see what your detach trailer button is

Try and find some guides from one of these websites...

http://www.neoseeker.com/Games/cheats/PC/hardtruck_18wheels.html

http://www.neoseeker.com/Games/Products/PC/hardtruck_18wheels/

http://www.cheatmasters.com/cheats/21866/Hard_Truck_18_Wheels_of_Steel_cheats.html

http://www.actiontrip.com/cheats/hardtruck18wheelsofsteel.phtml

http://www.transpointtrucking.com/wos.php

http://www.answers.com/topic/hard-truck-18-wheels-of-steel

Well I hope one of these Websites has the help you want.

Levi_xx