That message, that machine is well discussed. What I find is that folk are losing the knowledge to replace the cmos battery as well as losing the notes on what they set the BIOS to for the best speed.
I don't own this model but have fixed similar models too many times. The error is common at least as well as what to try next.
I have an old (ancient) AMD XP 2000+ based machine. It's been a while since it was turned on, it was in a box like 3 years... The first time I turned it on, to check if it's working, on boot screen I got the message "CMOS error, setup will load defaults" (or something like that). I pressed "enter" and when the winxp booted I went to the system properties. There I saw that the processor wasn't detected as AMD Athlon XP 2000+ 1,6GHz, but as AMD Athlon 1,24 GHz...
I wanted to give it away to brother's kids, to play with. But I don't want to find myself in situation that I gave them faulty PC. Could it break down completely and is there a way to fix this? I know I should probably replace BIOS battery, but I think that won't solve the processor speed issue...
MSI K7N2 Delta-L
AMD Athlon XP2000+ 1,6GHz