download sapphire trixx. underclock memory to 300 and start working your way up on the core clock.. start at 900.. if it crashes drop 15 if not go up 15 more. i have a dew of these cards.. one is stable at 985 the other 1015 maybe even more i havnt pushed it farther. windows guiminer -v -w256 -f1   sould get you in 300 Mhash ballpark,  -f1 will make your desktop lag a little so i turn that off if i need from time to time(remove setting stop miner and restart)