I have an older power supply with a -5v rail and an MSI K7N2-6570
motherboard. With this combination, the BIOS shows voltage on the -5v
rail, but if I put in a different power supply that doesn't even
support a -5v rail, I get 0.00 voltage in the BIOS. I know what you
are probably thinking, "duh! of course you won't see voltage if you
don't have the -5v rail.".

My question here is, if my newer power supply doesn't support the -5v
rail, and the motherboard is expecting it, will I have any problems?
The system ran fine through POST, and memtest x86, but it wasn't kept
on for much longer after that. What would the motherboard be
utilizing a-5v rail for? Will the motherboard malfunction without
this -5v rail? Any chance of damaging anything by not supply this -5v
rail?

TIA :)