Sorry but your wrong there, Raid must be disabled as it will be looking for the bootmgr of both the drives in raid mode, as they are paired as one drive essentially.
Raid should always be turned off as a fact since the minimum amount of drives to make a raid array is 2.
Since you only have one Hdd it should be turned off. And Sata interface should be set to Sata mode.
If you are booting from a dvd to install the new OS, then you will have to go into the bios and set the boot order of the devices. To do this press one of theses keys when you power the computer on Del key, F1 key, or the F2 key.
Once in the bios go to the boot options menu and you will see a list of devices the Dvd drive needs to be set to number one and the Hdd needs to be set to number two.
Save the settings in the bios and exit.
You should get a message on the next reboot to say "Press any key to boot from dvd drive". It may be the case that the windows 7 Disc is not a bootable version but has to run through windows to install or upgrade the system also. So a prior working os like xp may be needed Abbadon. Hope it helps