Old Desktop, now 16 years old.
well it is old and needs service as all do that old as in HARDware first.
the PC is 2006 old, a super relic now.
The Cmos battery this old is no good after 7 years. old.
so that be hopeless and makes BIOS go MAD just like you saw.
so replace it. for $1 , lane 15 CR2032 coin cell battery
then do this. 9 steps, next
https://www.pcdied.com/cmos.html#Reset_only.
next is that useless old 16 year old HDD,
we test it next, if bad no OS on earth will load or run there,
Impossible.! (like flat tire on a car same thing)
I use a linux boot dvd to run disktest, Ubuntu v20
more move the relic hdd to 2nd good PC and run this on that.
or just buy a SSD 128gb for $20 and end the HDD pain.....now.
10s seconds at run, and done.
https://www.passmark.com/products/diskcheckup/
100% free, safe and no ads or other junk here, pure GOLD
see free linux boot, run disk tests here.
https://www.pcdied.com/linux.html