I had a computer with windows 8.1 installed but the HDD died. So I bought a NEW one and installed windows 8.1 with SATA MODE IDE. Everything was fine UNTILL I shut it down. When I tired to open it said that there were no bootable device. I tried everything and FINALLY when I changed SATA mode to AHCI it saw the HDD but could not start Windows, so I changed it back to IDE and it started Widows as if nothing had happened.
Whenever I shut down the computer and try to start it, the same thing happens, and I do all these steps again.

I also tried to install windows 8.1 on AHCI mode, but the same thing happened again. But this time I had to switch to IDE and then AHCI again.

Also, when I pick restart option, not shut down, there is no problem. It RESTARTS just fine.

Do you have any idea why this is happening or how can I fix this?Set BIOS to IDE mode...wipe HDD and do a clean install...
For some reason BIOS isn't recognising changes made which is 1 of 2 things...not pressing F10 to "save changes and exit"...or CMOS battery may be goin flat.