In my experience with software voltage measurements, it is either way off or close enough to get a rough idea where it is at. If your 12V is displayed as 13V and your computer is still running, it's pretty obvious the program is reading the wrong sensor or calculating the voltage wrong. If it's in the ballpark of where it should be then it is programmed properly, but I wouldn't put too much value in the numbers. It's fine for a quick glance but if you are trying to see how well your PSU regulates voltages with different loads, it's useless to try and rely on software. Even a $10 multimeter will be much more accurate.
edit: And to the OP, we didn't forget about you. Assuming the software readings are in the ballpark, your 12Vrail is just fine. Even if the 12V rail wasn't fine, RAM is usually ran off the 3.3V rail. The state of the 12V won't have an affect on your RAM.