Depends on what kind of user it is. My BIOS can select the disk that will be first tried for boot, and within that which partition has priority. I can select th

Depends on what kind of user it is. My BIOS can select the disk that will be first tried for boot, and within that which partition has priority. I can select this during boot without setting it in the bios too. Another option is to use one of the boot disk on usb drive solutions. There are even alternative boot loaders (not windows or grub) that can search the disk for ALL bootable partitions.