[NAME]  Unfortunately, the BIOS setup options aren't listed in the online XPS 8900 service manual, so... Open BIOS setup and look around for an option to "Report keyboard errors". Assuming you find it, set it to disabled. Don't change any else in BIOS setup, but be sure to save the change to that option, if you made one, before exiting setup. When you exit setup, PC should boot automatically without any error messages, without needing the old keyboard connected. Just keep in mind you will have to connect that old keyboard again if you ever need to enter BIOS setup (F2), or if you need to use the F12 boot menu.
Inspiron XPS 8900 Windows 10 I have a Bluetooth keyboard and mouse. They work fine with this PC when windows 10 is running. But the keyboard is not detected on start up and gives an error screen in an infinite loop. So it seems the bIOS does not recognise Bluetooth. The Bluetooth mouse and keyboard work very well once Windows has loaded and I can login to Window with those devices. BUT to get to that point I must have either a wireless keyboard adapter in a usb port, or a wired keyboard in a usb port. The PC will then boot and present the Windows signon screen. From then the Bluetooth devices can be used (including for signon). But I cant boot without having an old keyboard available. Sort of defeats the purpose of using Bluetooth -- which was to save a usb port. Is there a workaround, or a BIOS update, that will allow the PC to detect the Bluetooth keyboard and proceed to boot?    
BIOS & Bluetooth