SATA HD recognized on IDE chanell

Hello!

I have recently bought HD Seagate SATA2 200g which my motherboard doesnt recognize as SATA disc. My MB is GA-8ipe1000pro-g and has Bios ver. F4.I have change my settings as following:boot sequence first cdrom, second SATA HD; onchip sata manually; SATA port 0 configure as "SATA port 0"
My harddisk is only recognized on IDE chanel in bios and on startup and when I loaded XP on it I have also installed sata drivers(which I got from a cd) and the disc was still on IDE controller. Otherwise it works fine and in disk management the status is healthy. I also want to know, why the current size of the disk is 186G instead of 200G.
Any help will be appreciated.
Thanks!