Force resolution kde

[Jordi Ferrando Fabra]

Hi,

I am setting a kubuntu 8.04 system, and I want to force the kde screen 
resolution at 1024x768.
I open systemsettings and select 1024x768, but as a user as an 
administrator.

The system, nevertheless, starts the kde login screen always at 
1280x1024, but it decreases the resolutiton to 1024x768 once the user 
logs into kde.

This is very annoying to me, does anyone know a fix?

Regards,
Jordi Ferrando