Need help reducing 12v dc to 8.7v dc

I'm kinda a newbie to electronics at least this aspect I do modifications for game consoles and got bored with that and decided to take it a little farther. My last project was such a great success that I wanted to see if there was room for improvement. I have 2 power sources and i want to reduce it to just the one, one it is an ATX power supply which I use 5v and 12v from the other is a 8.7v power adapter(from a playstation 2) so basically I want to eliminate the power adapter and stick with just the ATX power supply. Can someone point me in the right direction or help me with this Thankyou

depending on current needed

but simple method would be to use a 7809 voltage regulator and a diode.
get you about 8.5 from the 9v
or a zenier diode
or use an adjustable voltage regulator
there are numerous power supply circuits on the web some using adjustable voltage regulators.

lm317 adjustable reg would do....