Voltage Regulators in Computer Power Supply?
Computer supplies don't usually have integrated voltage regulators inside.  But they have all the necessary elements of a voltage regulator inside.  In a sense, the whole supply is a regulator.

There will be a voltage reference inside.  The output voltage (possibly scaled by a resistor divider) is compared to the voltage reference, and the supply is turned "up" or "down" to make it match the voltage reference.  The reference might be a TL431 or a 5.1V zener diode.

Computer supplies often regulate a main voltage (the 5V or 3.3V output) and arrange the other outputs to be ratios of the main one, by turns ratio on the transformer for example.  This is not really precise but works well enough for powering computers.