What miner are you using? If you're using CGminer from a shortcut, just at --gpu-memclock desired mem clock. For example, I use --gpu-memclock 300.
Thanks mate, I'll give that a shot; is there any way to adjust each of the cores individually?
To the others; I'm trying to get to 300mhz on all cores.
If I run the memory on 500mhz or 600mhz the pc becomes very prone to BSODs. Provided I dont touch it start anything or do anything I can (and do) run 500mhz on the 3 cores not powering the screen. with all 4 cores at 775 or 800 overnight.