Will PC3200 ram work in 1ghz Powerbook G4 12"

You can see if more memory will help for what you run by bringing up Activity Monitor, which is on your hard drive in applications/utilities. Look at the system memory tab at page ins and page outs. The system writes a page of memory out to the hard drive when memory is full and it needs to make room for something else. Too much of this can really impact performance. If page outs is 10% to 15% or more of page ins, you can use more memory.

While memory is generally supposed to be able to run at slower speeds the computer architecture supports, I would be hesitant to do that with your Powerbook. PowerBook architecture varies power on the bus's to control memory heat and help battery life. So memory that meets Apple specs still may not work. If you get the memory and have any issues, there's no solution, except to go with memory from vendors like Crucial, Kingston (not their value ram though), Samsung, and OWC, with memory specifically for your system. For example, here is what Crucial offers: http://www.crucial.com/store/listparts.aspx?model=PowerBook%20G4%201GHz%20(12-in ch%20Display)&Cat=RAM and here's what OWC has http://eshop.macsales.com/MyOWC/Upgrades.cfm?sort=pop&model=188&type=Memory