How to remove boot options from startup?

Whenever I boot my system and enter the startup menu, I have options from old drives that I no longer use. Even when no drives are connected, I still get a list of 6 boot options. Is there any way of removing these?

You can simply remove them by downloading the BIOS you are on and re-flash it. I've done this on a couple of my systems. Takes around a couple of minutes.
To do this format a USB flash drive in MS-DOS(FAT32). Copy over the unzipped version of your BIOS to the USB. Boot to the BIOS and use Q-Flash, locate the file from the USB drive. Thats it.