Recently reinstalled windows and have AHCI enabled (perhaps it has something to do with AHCI mode). Basically, I have the option now to eject my hard drives in the "Safely remove hardware and eject media" facility at the bottom right of the tray bar. Except that, I would not want to eject my operating system hard drive, and probably don't really want to eject my data hard drives at any time either. Is there any way to stop windows from giving me this option? I don't want it.
Since you didn't provide any specifics I'm going to hazard a guess:
You plugged your SATA drive into a port on the motherboard that's ear-marked for eSATA.
In turn the BIOS reports that is a removable device port, and Windows offers you the eject.
Try a different SATA port.
Otherwise, ensure you chipset drivers are fully-up-to-date and check your BIOS for options to flag those ports differently (this option is rare at best).