Load HBA driver under RIS installation

If the driver is not OS bundling , We can press “F6” to load extra storage driver while install OS in client machine which booted from Win2000 RIS Server .
But I setup a Win2003 RIS server , and client no choice to load extra driver while used PXE to boot up for WinXP RIS setup ; It can not work to press “F6” to load driver .
My question is how to load extra driver under OS Setup from Win2003 RIS Server .