Help me reduce power usage on this PC

Thanks all. I'll see what I can do, but it's possible I'll only replace the case. It's hard to find parts for this one

Layback Bear said:

Old computer parts are like old car parts. The people who have them no they are hard to come by so they raise the price.

When you get done replacing all the things in the computer to become more green you could just turn off a lamp and save the same amount or more of energy.

Don't get confused with power supplies. As long as it's a quality power supply and has more than enough watts your good.

It can be a 1000W power supply and if the computer only request 200W that is all the power supply will put out. The difference is the 1000W power supply will do it with ease therefore less draw from the wall socket.
It is so small that I doubt that most users would have meters to read such small changes.

Thanks. I'll keep the old PC as it is, it is perfect for my grandparents :)
Oh, and great post on the power supplies - very informative, I was always unsure about power supplies So thanks !