just saying, if the thing won’t even let you into the BIOS because it’s that bad, to try to play around, there is a way to get to that point.
*If you’ve set up custom settings in your BIOS you’ll need to be sure to re-do them
what you gotta do is open up the case, and find the memory reset pins, and jumper them (temporarily) to the reset setting, reboot, it should beep or something, then power it down, return the jumper to normal settings, and boot. then enter the bios and check in on the configurations, correct errors, and then try getting back to work on your drives (I.E. restoring the MBR to boot to previous windows installs, or clean installing, or whatever you’re motivated to do. Also, beware of the risk of losing any data on said drives during these processes.)