[CentOS] Small GRUB screen (menu/splash image)

Hi,

After moving my CentOS 6 installation over to a new PC, the GRUB 
start-up screen looks a bit strange. On the old machine, the menu area 
and splash image would cover the entire screen, but now they occupy only 
a small rectangle in its centre. I think what happens is that the max 
resolution of the graphics card/monitor combo is enabled even at this 
early stage, but GRUB assumes a 640x480 display.

Is there any way I can change the resolution so that the GRUB screen 
covers the entire display? I couldn't find anything related to this in 
the documentation, or when searching the web, or actually, the topic is 
mentioned a few places, but they all refer to GRUB 2, and CentOS 6 of 
course has (a patched version of) 0.97.

Thanks,

- Toralf