Shot in the dark here but

I recently found a stick of 512MB PC2700 DDR memory, I currently have 1GB (2x512) Corsair XMS memory. Now I was wondering if I could use this pc2700 module and have no issue. Thanks. Dang never mind I'll lose Dual Channel.

yea you can use it. only thing that will happen is that the bios will run all the sticks at the same speed of the slowest stick of ram. Meaning is you have 3 sticks of ddr 400 and 1 stick of say ddr 500 then the bios will run the ddr500 stick at ddr400. Also you may have to go through and manually configure ram timings.

I know that but I'll lose my dual channel, just not worth it.