PC3200 RAM is DDR memory that runs at 400 FSB. If you have PC3200 then its already at that speed. PC2100 runs at a 266mhz FSB, and PC2700 runs at a 333mhz FSB.
If you have either one of the others, PC2100 or PC2700, your new PC3200 will run with the older RAM, it will simply run at the speed of the slowest stick. Sounds to me like you dont have a compatibility issue, you have a quality issue. There is a program out there for testing RAM, but I'm too tired to think of it right now. Hopefully someone can link you to the download. If not, I'll come up with it in the morning.