I found this;
http://www.cpemma.co.uk/7volt.html

And I am wondering about any adverse effect on other components that may be powered by the same 5v supply.

 

Don't modify the power supply's harness. You can get extenders and "Y" splitters, and make the modificaiton on one of those; make sure you label the modified extender/"Y" splitter. Otherwise, if you forget and plug in something else later, you could wind up damaging lots of stuff.

If the fan plugs into the motherboard, don't attempt this mod.

 

I dont know whats the internal circuitry of the power supply exactly so i cant guaranty that is not going to cause problems. Also, i dont see the reason to run the fan at a lower voltage, you just reduce the airflow through the PC case and increase its temperature.

 

Well, it's just something I stumbled upon while looking for a very simple PWM for a 6 volt DC motor, it draws less than an amp, and the manufacture of the motor suggested that I use my 12 volt that is available and PWM it so the rms is about 6 or 7 volts.

I have 12 volts and 5 volts, so I was wondering about this little trick, but I am not sure what might happen to the other components I am powering with the 5 volt side which are 4 0-1 psi transducers.

I found your post, SgtWookie, on the PWM circuit and I might go with that one.

EDIT
Personally, I wouldn't do this to my Computers.