Can't get rid of SteamOS in boot menu

[Montague38]

I installed SteamOS when I first built my computer. I've changes the OS back to Windows for now, but when I use the boot menu I still see SteamOS as one of the selections. It didn't bother me at first but now I've changed the hard drive 2 times and reset the BIOS a few times and it's still there. Where would this menu item be hiding. I've pulled the battery, shorted the jumper, and used only a cleared USB stick to boot to Linux and it's still there.

Motherboard: ASUS H81m-c/csm i5 cpu 8 gigs of ram.

Where does the data come from for the boot menu list?

 

[Montague38]

I am using a completely new hard drive. I get the SteamOS menu listing even when I have no hard drives hooked up.