Game Resolution TroubleFollow

Hi, i have had some problems with setting game resolution, on my main system:

AMD XP2400+
Asus A7N8X Deluxe
1024 DDR
Radeon 9700 PRO
WIN XP (all updates)
Latest DirectX

and on my secondary system:

AMD Duron 1600
Gigabyte GA-7N400E
512 DDR
Radeon 8500
WIN XP (all updates)
Latest DirectX

When i install the game and enter options in order to setup my ingame resolution, there is only one choicethere and that is 1600x1200, the drop down menu doesn't open and therefore doesn't let me change to game resolution that i want to use. I've tried reinstalling the game several times and nothing changed.

Did anyone else come across the same problem, and how did you solve it.

Thank you for your answers.