RAID 5, windows/ubuntu server

Poweredge t110 ii server , with 4 hard disks controlled using RAID 5 ,OS was windows server 2008
first i used the dell CD and change the OS configuration to windows essential business then CD install some things, at reboot system asked for windows essential cd and it wasn't exist
i reboot again but this time from ubuntu cd and install the ubuntu in only one hard disk ( i wasn't know about RAID )
then at reboot system didn't see ubuntu and load windows and ask again for windows essential cd
i tried to reboot from dell cd again and install windows server 2008 again but dell cd failed to prepare it this time and ask for missing things

i want to know away to remove windows from all disks and instead install linux instead

thanks

#beginner