g4 Mini Ram backwards compatible?

I have a G4 1.25Ghz Mini computer that I use at work that has the 1 stick of 512MB of PC2700 DDR ram in it, and it gets slow when I have numerous apps open so I'd like to upgrade the ram to 1GB. I also have a bricked Dell Optiplex that is going to the dumpster that has two 1GB PC4200 DDR2 sticks in it, that I am going to harvest before trashing. I know the Mini can take faster PC3200 Ram, and that the Dells would work with slower PC3200 as well, but would the Mini work with one of the 1GB sticks of PC4200 - which would theoretically be 2x faster?? Even though it is DDR2 would it slow down and work at the DDR PC2700 bus speed or would it be unstable? I know overclocking causes instability and heat generation, but has anyone ever tried underclocking? I hate to pry the Mini open just to see so thought I'd see if anyone had done this before or knew offhand if it would work. Thanks!

DDR2 will not fit in a DDR slot. The little notch in the ram that keeps it from being put in backwards it about 1mm off on the DDR2 when compared with DDR. They will look very similar, but once you hold them together you will see that they are different.

If you had DDR that was faster than PC2700, that would clock down to PC2700 speeds and work fine. I used PC3200 for my mini because it was actually cheaper.

Cool. Thanks. I hadn't even thought of looking at the slots on the sticks. Oh well, it was a thought. Maybe I'll just try to sell those two 1GB PC4200 DDR2 sticks and get me a 1GB DDR stick in their place. Thanks again.