Hard drives and booting

Basically, installed win 7 then it kept crashing and freezing, so reinstalled it with just one hdd in. Works fine. When i shut it down and plug in my other 2 internal sata’s it boots up and comes up with 2 lines of:
Reboot and select proper boot device or insert boot media in selected…
Ive checked the bios to make sure theyre in the right order and theres no jumpers or anything needed for them. What am I doing wrong?
Thanks in advance
Answer #1

Ive checked the bios to make sure theyre in the right order

Then check again,It’s clearly not set right otherwise you wouldn’t be having this problem.
Answer #2
you also have to set which HDD is 1st
or just try swapping the the data cables on the drives
Answer #3
Go to BIOS, and change the Boot Sequence