Fixed Power Supply for LM317?

So maybe I'm over-thinking this but... Can i use a fixed power supply (like a computer PSU) to power a driver? (without modifying the PSU). I am working on a build using a standard linear LM317T driver to and a 638nm diode. I do not want to use batteries and portability isn't an issue. I understand that i will need 7.2 volts or so (3 for the driver , 3 for the diode , 1.2 for batteries mostly). From what i have read and understand ( I may be wrong), If i put a 12v supply into this driver, the excess voltage will just be dissipated as heat. Is this correct or will it damage the driver? Any tips on "plug into the wall" type of power supplies would be appreciated. Sorry in advance if this topic has been addressed somewhere else.

- Dan

Correct, correct, and correct.

Be sure to use adequate heat sinking and monitor the temperature. The LM317 has over-temp protection, but it's best not to push it. If it's too hot to touch, increase the heat sinking. Since you're using a high(ish) power red, you'll want to be sure your power supply is capable of at least 1A. The value stated on the power supply will be the rated max current - there is no problem using a 20A power supply to power a 500mA load for example. Ideally you want somewhere around 6-8V, but 12 should be fine, provided you monitor the temp. You can even feed it up to 35V if you feel like wasting energy