I have a computer with an SLI video card (not aware of exact model) and I have a CRT (NEC Multi-Synch FE990)

Today when I tried to boot up, after the BIOS screen and windows load, I get a message saying "Signal Frequency is out of Range -
FH = 49.4
FV = 39.6"

I've tried starting in safe mode and my moniter displays normally, however I don't know what setting to change to fix my problem

I also have attempted a system restore with windows- hasn't worked.

Can anyone help?