[CentOS] Centos4 and IBM x346

im triying to install linux on a IBM x346 thats uses the a320raid driver, this machines has 2 disk as a raid 1 (with W2003 Server)and a third disk for Centos4. 
when i install Centos its see 3 disk, no the raid, my question is, those grub depends on Linux seing the raid for properly bootup, because when i install grub in /dev/sda i does not load ok. 

Im triying to setup a dual boot machine as you can see. 

Thanks