DRAM frequency is the frequency of your system RAM. The best thing that you could do is buy a new computer because overclocking that ancient Netburst CPU probably won't make it much better.
If I had to guess, I'd think that a 1:1 ratio between the bus bandwidth and the RAM bandwidth would probably be ideal, but I'm nto sure for those old Netburst CPUs anymore. It's been a long while since I've worked with them.