You need to pass that parameter on boot so just add "vga=XXXxXXX" to your boot loader. If you use ntldr then I have no idea. If you use lilo or grub then just add one of the following to your boot line:

640x480 vga=769
800x600 vga=771
1024x768 vga=773
1280x1024 vga=775
1600x1200 vga=796

For example:

kernel (hd0,10)/boot/vmlinuz rw root=/dev/hda11 hdb=scsi apm=power-off nomce vga=791 lang=us