Which ram to add?

I just bought a new computer that has 1GB of ram installed. I want to increase the ram to 2GB. The new computer has (2) 512mb of pc3200 speed DDR SDRAM in it. I have in an older computer with (2) 512mb of pc2700 speed DDR SDRAM in it that is only about 3 months old. Can I add the 2700 to the 3200 ram? I know it should slow the 3200 down to the 2700 speed, right? Adding the extra gig of ram even at 2700 would be better than not adding any more ram even if it would run at 3200 at 1gb? Which is better, leave it the way it is at 3200 1GB ram? Or add the 2700 for 2GB of ram running total 2700 2GB. I know the best thing to do is get 1, hell, 4 sticks of 3200 1GB for the maximum 4GB the system can have. But in reallity money don't grow on trees. Since the older ram I have is only 3 months old I would like to use it but only if it will make an improvement in system speed over buying brand new ram. I hope I explained this well enough. If not, please ask questions. Thanks for any input

It depends on what your plans are for the systems you have there. If you are going to gaming or running large applications on the system equipped with the PC3200 memory you would want to stay with the faster memory. Instead of buying 4gb of memory for only one machine(pointless) simply buy 2gb for the best system there and run the two 512mb dimms on the older machine if it will run them. Often mixing memory can see problems.

But what would be better, to leave the ram where it is at 3200, or add the 2700 to the 3200 sticks? I won't do much gaming, just have the ram and wondered would there be any advantage in using it or would it make the system performance less than it would be to leave it the way it is?

I'd stick with 1GB@3200. If you don't do anything that needs a lot of RAM you're better off with more bandwidth than having more ram for the sake of having more ram.

By adding slower memory to the fastest supported already installed you would see a performance loss rather then any boost there. Without running demanding applications or geared for gaming the 1gb of PC3200 will actually see a better performance then mixing that with a different speed of memory even if the additional was faster. If you start running larger apps or have more running in the background at some point you would then increase by either adding another pair of 512mb PC3200s or swapping to larger dimms.