Memory Upgrade Question

Hi Everyone,Well Payday arrived for me on Friday (woohoo!) so next item on my shopping list is more memory.FS2004 is generally OK, but it suffers from stutters at busy detailed airports and dense cloud formations - especially when turning. So reading other posts, upgrading from 512MB Ram to 1024MB sounds like the right thing to do.But that's not the question. Currently I have 2 sticks of PC2100 256MB modules in my machine. Could I add a single stick of PC2700 512MB memory into the third slot? Or would it be safer to stick with PC2100 memory for the upgrade? My motherboard is the MSI KT3 Ultra 2, the manual says I can install upto 3GB of 184-pin modules PC2700, PC2100 or PC1600.My current specs:AMD Athlon XP 2100+512MB PC2100MSI GF4-Ti4200 64MB Graphics Card (44.03 drivers)MSI KT2 Ultra 2 Mobo80GB 7200 RPM hard diskAnthony Dyer