"at the startup" of what ?
devices needed for booting (disk driver [e.g. ide, scsi], root filesystem driver [e.g. ext3, reiser], keyboard, display, etc.) have to be compiled into your kernel or go to:
"man initrd" .. initrd - boot loader initialized RAM disk
other devices (once you can access a disk during the boot process and load modules)
"man modules.conf" - configuration file for loading kernel modules